Positive resist composition, method of forming resist pattern, and polymeric compound

ABSTRACT

A positive resist composition including a base component (A) which exhibits increased solubility in an alkali developing solution under action of acid and an acid-generator component (B) which generates acid upon exposure, the base component (A) including a polymeric compound (A1′) containing an acid dissociable, dissolution inhibiting group within the structure thereof and including a structural unit (a0) represented by general formula (a0-1) (R 2  represents a divalent linking group, and A″ represents an oxygen atom, a sulfur atom, or an alkylene group of 1 to 5 carbon atoms which may contain an oxygen atom or a sulfur atom) and a structural unit (a2) derived from an acrylate ester containing a lactone-containing cyclic group; or a polymeric compound (A1) including the structural unit (a0) and a structural unit (a1) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group.

TECHNICAL FIELD

The present invention relates to a novel polymeric compound which can be used as a base component for a positive resist composition, a positive resist composition containing the polymeric compound, and a method of forming a resist pattern using the positive resist composition.

Priority is claimed on Japanese Patent Application Nos. 2008-251597 and 2008-251598, filed Sep. 29, 2008, and Japanese Patent Application No. 2008-254847, filed Sep. 30, 2008, the contents of which are incorporated herein by reference.

BACKGROUND ART

In lithography techniques, for example, a resist film composed of a resist material is formed on a substrate, and the resist film is subjected to selective exposure of radial rays such as light or electron beam through a mask having a predetermined pattern, followed by development, thereby forming a resist pattern having a predetermined shape on the resist film.

A resist material in which the exposed portions become soluble in a developing solution is called a positive-type, and a resist material in which the exposed portions become insoluble in a developing solution is called a negative-type.

In recent years, in the production of semiconductor elements and liquid crystal display elements, advances in lithography techniques have lead to rapid progress in the field of pattern miniaturization.

Typically, these miniaturization techniques involve shortening the wavelength of the exposure light source. Conventionally, ultraviolet radiation typified by g-line and i-line radiation has been used, but nowadays KrF excimer lasers and ArF excimer lasers are starting to be introduced in mass production. Furthermore, research is also being conducted into lithography techniques that use an exposure light source having a wavelength shorter than these excimer lasers, such as F₂ excimer lasers, electron beam, extreme ultraviolet radiation (EUV), and X-ray.

Resist materials for use with these types of exposure light sources require lithography properties such as a high resolution capable of reproducing patterns of minute dimensions, and a high level of sensitivity to these types of exposure light sources.

As a resist material that satisfies these conditions, a chemically amplified composition is used, which includes a base material component that exhibits a changed solubility in an alkali developing solution under the action of acid and an acid generator that generates acid upon exposure.

For example, a chemically amplified positive resist contains, as a base component (base resin), a resin which exhibits increased solubility in an alkali developing solution under action of acid, and an acid generator is typically used. If the resist film formed using the resist composition is selectively exposed during formation of a resist pattern, then within the exposed portions, acid is generated from the acid generator, and the action of this acid causes an increase in the solubility of the resin component in an alkali developing solution, making the exposed portions soluble in the alkali developing solution.

Currently, resins that contain structural units derived from (meth)acrylate esters within the main chain (acrylic resins) are now widely used as base resins for resists that use ArF excimer laser lithography, as they exhibit excellent transparency in the vicinity of 193 nm (for example, see Patent Document 1). Here, the term “(meth)acrylic acid” is a generic term that includes either or both of acrylic acid having a hydrogen atom bonded to the α-position and methacrylic acid having a methyl group bonded to the α-position. The term “(meth)acrylate ester” is a generic term that includes either or both of the acrylate ester having a hydrogen atom bonded to the α-position and the methacrylate ester having a methyl group bonded to the α-position. The term “(meth)acrylate” is a generic term that includes either or both of the acrylate having a hydrogen atom bonded to the α-position and the methacrylate having a methyl group bonded to the α-position.

Further, in order to improve various lithography properties, a base resin having a plurality of structural units is currently used for a chemically amplified resist. For example, in the case of a positive resist, a base resin containing a structural unit having an acid dissociable, dissolution inhibiting group that is dissociated by the action of acid generated from the acid generator, a structural unit having a polar group such as a hydroxyl group, a structural unit having a lactone structure, and the like is typically used. Among these structural units, a structural unit having a lactone structure is generally considered as being effective in improving the adhesion between the resist film and the substrate, and increasing the compatibility with an alkali developing solution, thereby contributing to improvement in various lithography properties.

DOCUMENTS OF RELATED ART Patent Documents

-   [Patent Document 1] Japanese Unexamined Patent Application, First     Publication No. 2003-241385 -   [Patent Document 2] Japanese Unexamined Patent Application, First     Publication No. 2006-016379

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

As further progress is made in lithography techniques and the application field for lithography techniques expands, development of a novel material for use in lithography will be desired. For example, as miniaturization of resist patterns progress, improvement will be demanded for resist materials with respect to various lithography properties such as resolution and the like.

The pattern shape is one of such lithography properties. In the formation of a resist pattern using a conventional resist composition, when the mask size (e.g., the hole diameter of a hole pattern, or the line width of a line and space pattern) is changed, the amount of light irradiated on exposed portions is changed. As a result, pattern collapse of the formed pattern is likely to occur. Such a problem is likely to occur in the formation of a fine pattern with a narrow pitch. For example, when a hole pattern having a hole diameter of about no more than 100 nm is formed, the circularity of the holes is likely to be deteriorated, and improvement thereof has been demanded.

The present invention takes the above circumstances into consideration, with an object of providing a novel polymeric compound which can be used as a base component for a positive resist composition, a compound useful as a monomer for the polymeric compound, a positive resist composition containing the polymeric compound, and a method of forming a resist pattern using the positive resist composition.

Means for Solving the Problems

For solving the above-mentioned problems, the present invention employs the following aspects.

Specifically, a first aspect of the present invention is a positive resist composition including a base component (A) which exhibits increased solubility in an alkali developing solution under action of acid and an acid-generator component (B) which generates acid upon exposure,

the base component (A) including a polymeric compound (A1′) containing an acid dissociable, dissolution inhibiting group within the structure thereof and including a structural unit (a0) represented by general formula (a0-1) shown below and a structural unit (a2) derived from an acrylate ester containing a lactone-containing cyclic group exclusive of the structural unit (a0); or a polymeric compound (A1) including a structural unit (a0) represented by general formula (a0-1) shown below and a structural unit (a1) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group exclusive of the structural unit (a0) and the structural unit (a2).

In the formula, R¹ represents a hydrogen atom, a lower alkyl group or a halogenated lower alkyl group; R² represents a divalent linking group; each R′ independently represents a hydrogen atom, an alkyl group of 1 to 6 carbon atoms, an alkoxy group of 1 to 6 carbon atoms or —COOR″, wherein R″ represents a hydrogen atom or an alkyl group; and A″ represents an oxygen atom, a sulfur atom, or an alkylene group of 1 to 5 carbon atoms which may contain an oxygen atom or a sulfur atom.

A second aspect of the present invention is a method of forming a resist pattern, including applying a positive resist composition according to the first aspect to a substrate to form a resist film, subjecting the resist film to exposure, and subjecting the resist film to alkali developing to form a resist pattern.

A third aspect of the present invention is a polymeric compound including a component (A1′) containing an acid dissociable, dissolution inhibiting group within the structure thereof and including a structural unit (a0) represented by general formula (a0-1) shown below and a structural unit (a2) derived from an acrylate ester containing a lactone-containing cyclic group exclusive of the structural unit (a0); or a component (A1) including a structural unit (a0) represented by general formula (a0-1) shown below and a structural unit (a1) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group exclusive of the structural unit (a0) and the structural unit (a2).

In the formula, R¹ represents a hydrogen atom, a lower alkyl group or a halogenated lower alkyl group; R² represents a divalent linking group; each R′ independently represents a hydrogen atom, an alkyl group of 1 to 6 carbon atoms, an alkoxy group of 1 to 6 carbon atoms or —COOR″, wherein R″ represents a hydrogen atom or an alkyl group; and A″ represents an oxygen atom, a sulfur atom, or an alkylene group of 1 to 5 carbon atoms which may contain an oxygen atom or a sulfur atom.

In the present description and claims, the term “aliphatic” is a relative concept used in relation to the term “aromatic”, and defines a group or compound that has no aromaticity.

The term “alkyl group” includes linear, branched or cyclic, monovalent saturated hydrocarbon, unless otherwise specified.

The term “alkylene group” includes linear, branched or cyclic divalent saturated hydrocarbon, unless otherwise specified. The same applies for the alkyl group within an alkoxy group.

A “halogenated alkyl group” is a group in which part or all of the hydrogen atoms of an alkyl group is substituted with halogen atoms. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms and iodine atoms.

A “fluorinated alkyl group” or a “fluorinated alkylene group” is a group in which part or all of the hydrogen atoms of an alkyl group or an alkylene group have been substituted with a fluorine atom.

The term “structural unit” refers to a monomer unit that contributes to the formation of a polymeric compound (resin, polymer, copolymer).

A “structural unit derived from an acrylate ester” refers to a structural unit that is formed by the cleavage of the ethylenic double bond of an acrylate ester.

The term “acrylate ester” is a generic term that includes acrylate esters having a hydrogen atom bonded to the carbon atom on the α-position, and acrylate esters having a substituent (an atom other than a hydrogen atom or a group) bonded to the carbon atom on the α-position. Examples of the substituent bonded to the carbon atom on the α-position include an alkyl group of 1 to 5 carbon atoms, a halogenated alkyl group of 1 to 5 carbon atoms and a hydroxyalkyl group.

Hereafter, an alkyl group of 1 to 5 carbon atoms and a halogenated alkyl group of 1 to 5 carbon atoms are frequently referred to as a lower alkyl group and a halogenated lower alkyl group, respectively. A carbon atom on the α-position of an acrylate ester refers to the carbon atom bonded to the carbonyl group, unless specified otherwise.

The term “exposure” is used as a general concept that includes irradiation with any form of radiation.

Effects of the Invention

According to the present invention, there are provided a novel polymeric compound which can be used as a base component for a positive resist composition, a positive resist composition containing the polymeric compound, and a method of forming a resist pattern using the positive resist composition.

BEST MODE FOR CARRYING OUT THE INVENTION

<<Positive Resist Composition>>

The positive resist composition of the present invention (hereafter, frequently referred to simply as “resist composition”) includes a base component (A) (hereafter, referred to as “component (A)”) which exhibits increased solubility in an alkali developing solution under action of acid and an acid-generator component (B) (hereafter, referred to as “component (B)”) which generates acid upon exposure.

In the positive resist composition, when radial rays are irradiated (when exposure is conducted), acid is generated from the component (B), and the solubility of the component (A) in an alkali developing solution is increased by the action of the generated acid. Therefore, in the formation of a resist pattern, by conducting selective exposure of a resist film formed by using the positive resist composition of the present invention, the solubility of the exposed portions in an alkali developing solution is increased, whereas the solubility of the unexposed portions in an alkali developing solution is unchanged, and hence, a resist pattern can be formed by alkali developing.

Here, the term “base component” refers to an organic compound capable of forming a film. As the base component, an organic compound having a molecular weight of 500 or more can be preferably used. When the organic compound has a molecular weight of 500 or more, the film-forming ability is improved, and a resist pattern of nano level can be easily formed.

The “organic compound having a molecular weight of 500 or more” which can be used as a base component is broadly classified into non-polymers and polymers.

In general, as a non-polymer, any of those which have a molecular weight in the range of 500 to less than 4,000 is used. Hereafter, a non-polymer having a molecular weight in the range of 500 to less than 4,000 is referred to as a low molecular weight compound.

As a polymer, any of those which have a molecular weight of 2,000 or more is used. Hereafter, a polymer having a molecular weight of 2,000 or more is referred to as a polymeric compound. With respect to a polymeric compound, the “molecular weight” is the weight average molecular weight in terms of the polystyrene equivalent value determined by gel permeation chromatography (GPC). Hereafter, a polymeric compound is frequently referred to simply as a “resin”.

<Component (A)>

[Polymeric Compound (A1) and Polymeric Compound (A1′)]

In the positive resist composition of the present invention, the component (A) includes the polymeric compound (A1) or the polymeric compound (A1′).

The polymeric compound (A1′) (hereafter, referred to as “component (A1′)”) includes a structural unit (a0) represented by general formula (a0-1) and a structural unit (a2) derived from an acrylate ester containing a lactone-containing cyclic group exclusive of the structural unit (a0), and the polymeric compound (A1′) contains an acid dissociable, dissolution inhibiting group within the structure thereof.

The component (A1′) preferably includes a structural unit (a1) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group, as well as the structural units (a0) and (a2).

Furthermore, the component (A1′) preferably includes a structural unit (a3) derived from an acrylate ester containing a polar group-containing aliphatic hydrocarbon group, as well as the structural units (a0) and (a2), or the structural units (a0), (a1) and (a2).

The polymeric compound (A1) (hereafter, referred to as “component (A1)”) includes a structural unit (a0) represented by general formula (a0-1) and a structural unit (a1) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group exclusive of the structural unit (a0) and the structural unit (a2).

The component (A1) preferably includes the aforementioned structural unit (a2), as well as the structural units (a0) and (a1).

Furthermore, the component (A1) preferably includes the aforementioned structural unit (a3), as well as the structural units (a0) and (a1), or the structural units (a0), (a1) and (a2).

(Structural Unit (a0))

In formula (a0-1), R¹ represents a hydrogen atom, a lower alkyl group or a halogenated lower alkyl group.

The lower alkyl group for R¹ is preferably a linear or branched alkyl group of 1 to 5 carbon atoms, and specific examples include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a tert-butyl group, a pentyl group, an isopentyl group, and a neopentyl group.

The halogenated lower alkyl group for R¹ is a group in which part of or all of the hydrogen atoms of the aforementioned alkyl group is substituted with halogen atoms. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms and iodine atoms, and fluorine atoms are particularly desirable.

As R¹, a hydrogen atom, a lower alkyl group or a fluorinated alkyl group is preferable, and a hydrogen atom or a methyl group is particularly desirable in terms of industrial availability.

In general formula (a0-1), R² a divalent linking group.

Preferable examples of R² include a divalent hydrocarbon group which may have a substituent, and a divalent linking group containing a hetero atom.

A hydrocarbon “has a substituent” means that part or all of the hydrogen atoms within the hydrocarbon group is substituted with groups or atoms other than hydrogen atom.

The hydrocarbon group may be either an aliphatic hydrocarbon group or an aromatic hydrocarbon group. An “aliphatic hydrocarbon group” refers to a hydrocarbon group that has no aromaticity.

The aliphatic hydrocarbon group may be saturated or unsaturated. In general, the aliphatic hydrocarbon group is preferably saturated.

As specific examples of the aliphatic hydrocarbon group, a linear or branched aliphatic hydrocarbon group, and an aliphatic hydrocarbon group containing a ring in the structure thereof can be given.

The linear or branched aliphatic hydrocarbon group preferably has 1 to 10 carbon atoms, more preferably 1 to 8, still more preferably 1 to 5, and most preferably 1 or 2.

As the linear aliphatic hydrocarbon group, a linear alkylene group is preferable. Specific examples thereof include a methylene group [—CH₂—], an ethylene group [—(CH₂)₂—], a trimethylene group [—(CH₂)₃—], a tetramethylene group [—(CH₂)₄-—] and a pentamethylene group [—(CH₂)₅—].

As a branched aliphatic hydrocarbon group, a branched alkylene group is preferable, and specific examples include alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)—, and —C(CH₂CH₃)₂—; alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; alkyltrimethylene groups such as —CH(CH₃)CH₂CH₂—, and —CH₂CH(CH₃)CH₂—; and alkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂—, and —CH₂CH(CH₃)CH₂CH₂—. As the alkyl group within the alkylalkylene group, a linear alkyl group of 1 to 5 carbon atoms is preferable.

The linear or branched aliphatic hydrocarbon group (chain-like aliphatic hydrocarbon group) may or may not have a substituent. Examples of substituents include a fluorine atom, a fluorinated lower alkyl group of 1 to 5 carbon atoms, and an oxygen atom (═O).

As examples of the hydrocarbon group containing a ring in the structure thereof, a cyclic aliphatic hydrocarbon group (a group in which two hydrogen atoms have been removed from an aliphatic hydrocarbon ring), and a group in which the cyclic aliphatic hydrocarbon group is bonded to the terminal of the aforementioned chain-like aliphatic hydrocarbon group or interposed within the aforementioned chain-like aliphatic hydrocarbon group, can be given.

The cyclic aliphatic hydrocarbon group preferably has 3 to 20 carbon atoms, and more preferably 3 to 12 carbon atoms.

The cyclic aliphatic hydrocarbon group may be either a polycyclic group or a monocyclic group. As the monocyclic group, a group in which two hydrogen atoms have been removed from a monocycloalkane of 3 to 6 carbon atoms is preferable. Examples of the monocycloalkane include cyclopentane and cyclohexane.

As the polycyclic group, a group in which two hydrogen atoms have been removed from a polycycloalkane of 7 to 12 carbon atoms is preferable. Examples of the polycycloalkane include adamantane, norbornane, isobornane, tricyclodecane and tetracyclododecane.

The cyclic aliphatic hydrocarbon group may or may not have a substituent. Examples of substituents include a lower alkyl group of 1 to 5 carbon atoms, a fluorine atom, a fluorinated lower alkyl group of 1 to 5 carbon atoms, and an oxygen atom (═O).

With respect to a divalent linking group containing a hetero atom, a hetero atom is an atom other than carbon and hydrogen, and examples thereof include an oxygen atom, a nitrogen atom, a sulfur atom and a halogen atom.

Specific examples of the divalent linking group containing a hetero atom include divalent non-hydrocarbon groups containing a hetero atom, such as —O—, —C(═O)—, —C(═O)—O—, a carbonate bond (—O—C(═O)—O—), —S—, —S(═O)₂—, —S(═O)₂—O—, —NH—, —NR⁰⁴—(R⁰⁴ represents a substituent such as an alkyl group or an acyl group), —NH—C(═O)—, and ═N—. Further, a combination of any one of these “divalent non-hydrocarbon groups containing a hetero atom” with a divalent hydrocarbon group can also be used. As examples of the divalent hydrocarbon group, the same groups as those described above for the hydrocarbon group which may have a substituent can be given, and a linear or branched aliphatic hydrocarbon group is preferable.

R² may or may not have an acid dissociable portion in the structure thereof. An “acid dissociable portion” refers to a portion within the organic group which is dissociated from the organic group by action of acid generated upon exposure. When R² group has an acid dissociable portion, it preferably has an acid dissociable portion having a tertiary carbon atom.

In the present invention, as the divalent linking group for R², an alkylene group, a divalent aliphatic cyclic group or a divalent linking group containing a hetero atom is preferable. Among these, an alkylene group is particularly desirable.

When R² represents an alkylene group, it preferably has 1 to 10 carbon atoms, more preferably 1 to 6, still more preferably 1 to 4, and most preferably 1 to 3. Specific examples of alkylene groups include the aforementioned linear alkylene groups and branched alkylene groups.

When R² represents a divalent aliphatic cyclic group, as the aliphatic cyclic group, the same aliphatic cyclic groups as those described above for the “aliphatic hydrocarbon group containing a ring in the structure thereof” can be used.

As the aliphatic cyclic group, a group in which two hydrogen atoms have been removed from cyclopentane, cyclohexane, norbornane, isobornane, adamantane, tricyclodecane or tetracyclododecane is particularly desirable.

When R² represents a divalent linking group containing a hetero atom, preferable examples of linking groups include —O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NH— (H may be replaced with a substituent such as an alkyl group, an acyl group or the like), —S—, —S(═O)₂—, —S(═O)₂—O—, a group represented by the formula -A-O—B—, and a group represented by the formula -[A-C(═O)—O]_(m)—B—. Herein, each of A and B independently represents a divalent hydrocarbon group which may have a substituent, and m represents an integer of 0 to 3.

When R² represents —NH—, H may be replaced with a substituent such as an alkyl group, an acyl group or the like. The substituent (an alkyl group, an acyl group or the like) preferably has 1 to 10 carbon atoms, more preferably 1 to 8, and most preferably 1 to 5.

In the group represented by the formula -A-O—B— or -[A—C(═O)—O]_(m)—B—, each of A and B independently represents a divalent hydrocarbon group which may have a substituent.

Examples of divalent hydrocarbon groups for A and B which may have a substituent include the same groups as those described above for the “divalent hydrocarbon group which may have a substituent” usable as R².

As A, a linear aliphatic hydrocarbon group is preferable, more preferably a linear alkylene group, still more preferably a linear alkylene group of 1 to 5 carbon atoms, and a methylene group or an ethylene group is particularly desirable.

As B, a linear or branched aliphatic hydrocarbon group is preferable, and a methylene group, an ethylene group or an alkylmethylene group is more preferable. The alkyl group within the alkylmethylene group is preferably a linear alkyl group of 1 to 5 carbon atoms, more preferably a linear alkyl group of 1 to 3 carbon atoms, and most preferably a methyl group.

In the group represented by the formula -[A-C(═O)—O]_(m)—B—, m represents an integer of 0 to 3, preferably an integer of 0 to 2, more preferably 0 or 1, and most preferably 1.

In general formula (a0-1), A″ represents an oxygen atom (—O—), a sulfur atom (—S—), or an alkylene group of 1 to 5 carbon atoms which may contain an oxygen atom (—O—) or a sulfur atom (—S—).

As the alkylene group of 1 to 5 carbon atoms for A″, a linear or branched alkylene group is preferable, and examples thereof include a methylene group, an ethylene group, an n-propylene group and an isopropylene group.

Examples of alkylene groups that contain an oxygen atom or a sulfur atom include the aforementioned alkylene groups in which —O— or —S— is bonded to the terminal of the alkylene group or interposed within the alkyl group. Specific examples of such alkylene groups include —O—CH₂—, —CH₂—O—CH₂—, —S—CH₂—, and —CH₂—S—CH₂—.

As A″, an alkylene group of 1 to 5 carbon atoms or —O— is preferable, more preferably an alkylene group of 1 to 5 carbon atoms, and most preferably a methylene group.

In general formula (a0-1), each R′ independently represents a hydrogen atom, an alkyl group of 1 to 6 carbon atoms, an alkoxy group of 1 to 6 carbon atoms or —COOR″.

The alkyl group for R′ is preferably a linear alkyl group or a branched alkyl group. Specific examples include a methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, tert-butyl group, pentyl group, isopentyl group, neopentyl group and hexyl group. Among these, a methyl group or ethyl group is preferable, and a methyl group is particularly desirable.

The alkoxy group for R′ is preferably a linear alkoxy group or a branched alkoxy group. Specific examples of the alkoxy groups include the aforementioned alkyl groups for R′ having an oxygen atom (—O—) bonded thereto.

In the formula —COOR″, R″ represents a hydrogen atom or an alkyl group.

The alkyl group for R″ may be linear, branched or cyclic, and preferably has 1 to 15 carbon atoms.

When R″ represents a linear or branched alkyl group, it is preferably an alkyl group of 1 to 10 carbon atoms, more preferably an alkyl group of 1 to 5 carbon atoms, and most preferably a methyl group or an ethyl group.

When R″ is a cyclic alkyl group (cycloalkyl group), it preferably has 3 to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and most preferably 5 to 10 carbon atoms. As examples of the cycloalkyl group, groups in which one or more hydrogen atoms have been removed from a monocycloalkane or a polycycloalkane such as a bicycloalkane, tricycloalkane or tetracycloalkane, which may or may not be substituted with a fluorine atom or a fluorinated alkyl group, may be used.

Specific examples include groups in which one or more hydrogen atoms have been removed from a monocycloalkane such as cyclopentane and cyclohexane; and groups in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane or tetracyclododecane.

In general formula (a0-1), the two R′ may be the same or different from each other

In terms of industrial availability, R′ is preferably a hydrogen atom or an alkoxy group

Specific examples of the structural unit (a0) are shown below.

In the formulas, R¹ and A″ are the same as defined above; and R²′ represents a linear or branched alkylene group.

The linear or branched alkylene group for R²′ preferably has 1 to 10 carbon atoms, more preferably 1 to 8, still more preferably 1 to 5, still more preferably 1 to 3, and most preferably 1 or 2.

A″ is preferably a methylene group, an oxygen atom (—O—) or a sulfur atom (—S—), and is most preferably a methylene group.

As the structural unit (a0), one type of structural unit may be used alone, or two or more types of structural units may be used in combination.

In terms of achieving excellent properties with respect to MEF, the shape of a formed resist pattern, in-plane uniformity (CDU), line width roughness (LWR) and the like in the formation of a resist pattern using a positive resist composition containing the component (A1) or (A1′), the amount of the structural unit (a0) within the component (A1) or (A1′), based on the combined total of all structural units constituting the component (A1) or (A1′) is preferably 1 to 60 mol %, more preferably 5 to 50 mol %, still more preferably 10 to 40 mol %, and most preferably 15 to 30 mol %.

(Structural Unit (a1))

The structural unit (a1) is a structural unit derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group which does not fall under the category of the aforementioned structural unit (a0) and the structural unit (a2) described later.

The structural unit (a1) “does not fall under the category of the aforementioned structural units (a0) and (a2)” means that a structural unit which falls under the category of the aforementioned structural unit (a0) or (a2) and contains an acid dissociable, dissolution inhibiting group is not a structural unit (a1).

As the acid dissociable, dissolution inhibiting group in the structural unit (a1), any of the groups that have been proposed as acid dissociable, dissolution inhibiting groups for the base resins of chemically amplified resists can be used, provided the group has an alkali dissolution-inhibiting effect that renders the entire component (A1) or (A1′) insoluble in an alkali developing solution prior to dissociation, and then following dissociation by action of acid, increases the solubility of the entire component (A1) or (A1′) in the alkali developing solution. Generally, groups that form either a cyclic or chain-like tertiary alkyl ester with the carboxyl group of the (meth)acrylic acid, and acetal-type acid dissociable, dissolution inhibiting groups such as alkoxyalkyl groups are widely known. Here, the term “(meth)acrylate ester” is a generic term that includes either or both of the acrylate ester having a hydrogen atom bonded to the α-position and the methacrylate ester having a methyl group bonded to the α-position.

Here, a tertiary alkyl ester describes a structure in which an ester is formed by substituting the hydrogen atom of a carboxyl group with a chain-like or cyclic tertiary alkyl group, and a tertiary carbon atom within the chain-like or cyclic tertiary alkyl group is bonded to the oxygen atom at the terminal of the carbonyloxy group (—C(O)—O—). In this tertiary alkyl ester, the action of acid causes cleavage of the bond between the oxygen atom and the tertiary carbon atom.

The chain-like or cyclic alkyl group may have a substituent.

Hereafter, for the sake of simplicity, groups that exhibit acid dissociability as a result of the formation of a tertiary alkyl ester with a carboxyl group are referred to as “tertiary alkyl ester-type acid dissociable, dissolution inhibiting groups”.

Examples of tertiary alkyl ester-type acid dissociable, dissolution inhibiting groups include aliphatic branched, acid dissociable, dissolution inhibiting groups and aliphatic cyclic group-containing acid dissociable, dissolution inhibiting groups.

The term “aliphatic branched” refers to a branched structure having no aromaticity. The “aliphatic branched, acid dissociable, dissolution inhibiting group” is not limited to be constituted of only carbon atoms and hydrogen atoms (not limited to hydrocarbon groups), but is preferably a hydrocarbon group. Further, the “hydrocarbon group” may be either saturated or unsaturated, but is preferably saturated.

As an example of the aliphatic branched, acid dissociable, dissolution inhibiting group, for example, a group represented by the formula —C(R⁷¹)(R⁷²)(R⁷³) can be given (in the formula, each of R⁷¹ to R⁷³ independently represents a linear alkyl group of 1 to 5 carbon atoms). The group represented by the formula —C(R⁷¹)(R⁷²)(R⁷³) preferably has 4 to 8 carbon atoms, and specific examples include a tert-butyl group, a 2-methyl-2-butyl group, a 2-methyl-2-pentyl group and a 3-methyl-3-pentyl group. Among these, a tert-butyl group is particularly desirable.

The term “aliphatic cyclic group” refers to a monocyclic group or polycyclic group that has no aromaticity.

The “aliphatic cyclic group” within the structural unit (a1) may or may not have a substituent. Examples of substituents include lower alkyl groups of 1 to 5 carbon atoms, lower alkoxy groups of 1 to 5 carbon atoms, fluorine atom, fluorinated lower alkyl groups of 1 to 5 carbon atoms, and oxygen atom (═O).

The basic ring of the “aliphatic cyclic group” exclusive of substituents is not limited to be constituted from only carbon and hydrogen (not limited to hydrocarbon groups), but is preferably a hydrocarbon group. Further, the “hydrocarbon group” may be either saturated or unsaturated, but is preferably saturated. Furthermore, the “aliphatic cyclic group” is preferably a polycyclic group.

As such aliphatic cyclic groups, groups in which one or more hydrogen atoms have been removed from a monocycloalkane or a polycycloalkane such as a bicycloalkane, tricycloalkane or tetracycloalkane which may or may not be substituted with a lower alkyl group, a fluorine atom or a fluorinated lower alkyl group, may be used. Specific examples include groups in which one or more hydrogen atoms have been removed from a monocycloalkane such as cyclopentane or cyclohexane; and groups in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane or tetracyclododecane. Further, these groups in which one or more hydrogen atoms have been removed from a monocycloalkane and groups in which one or more hydrogen atoms have been removed from a polycycloalkane may have part of the carbon atoms constituting the ring replaced with an ethereal oxygen atom (—O—).

Examples of acid dissociable, dissolution inhibiting groups containing an aliphatic cyclic group include (i) a group which has a tertiary carbon atom on the ring structure of a monovalent aliphatic cyclic group; and (ii) a group which has a branched alkylene group containing a tertiary carbon atom, and a monovalent aliphatic cyclic group to which the tertiary carbon atom is bonded.

Specific examples of (i) a group which has a tertiary carbon atom on the ring structure of a monovalent aliphatic cyclic group include groups represented by general formulas (1-1) to (1-9) shown below.

Specific examples of (ii) a group which has a branched alkylene group containing a tertiary carbon atom, and a monovalent aliphatic cyclic group to which the tertiary carbon atom is bonded include groups represented by general formulas (2-1) to (2-6) shown below.

In the formulas above, R¹⁴ represents an alkyl group; and g represents an integer of 0 to 8.

In the formulas above, each of R¹⁵ and R¹⁶ independently represents an alkyl group.

As the alkyl group for R¹⁴, a linear or branched alkyl group is preferable.

The linear alkyl group preferably has 1 to 5 carbon atoms, more preferably 1 to 4, and still more preferably 1 or 2. Specific examples include a methyl group, an ethyl group, an n-propyl group, an n-butyl group and an n-pentyl group. Among these, a methyl group, an ethyl group or an n-butyl group is preferable, and a methyl group or an ethyl group is more preferable.

The branched alkyl group preferably has 3 to 10 carbon atoms, and more preferably 3 to 5. Specific examples of such branched alkyl groups include an isopropyl group, an isobutyl group, a tert-butyl group, an isopentyl group and a neopentyl group, and an isopropyl group is particularly desirable.

g is preferably an integer of 0 to 3, more preferably 1 to 3, and still more preferably 1 or 2.

As the alkyl group for R¹⁵ and R¹⁶, the same alkyl groups as those for R¹⁴ can be used.

In formulas (1-1) to (1-9) and (2-1) to (2-6), part of the carbon atoms constituting the ring may be replaced with an ethereal oxygen atom (—O—).

Further, in formulas (1-1) to (1-9) and (2-1) to (2-6), one or more of the hydrogen atoms bonded to the carbon atoms constituting the ring may be substituted with a substituent. Examples of substituents include a lower alkyl group, a fluorine atom and a fluorinated alkyl group.

An “acetal-type acid dissociable, dissolution inhibiting group” generally substitutes a hydrogen atom at the terminal of an alkali-soluble group such as a carboxy group or hydroxyl group, so as to be bonded with an oxygen atom. When acid is generated upon exposure, the generated acid acts to break the bond between the acetal-type acid dissociable, dissolution inhibiting group and the oxygen atom to which the acetal-type, acid dissociable, dissolution inhibiting group is bonded.

Examples of acetal-type acid dissociable, dissolution inhibiting groups include groups represented by general formula (p1) shown below.

In the formula, R¹′ and R²′ each independently represent a hydrogen atom or a lower alkyl group; n represents an integer of 0 to 3; and Y represents a lower alkyl group or an aliphatic cyclic group.

In general formula (p1) above, n is preferably an integer of 0 to 2, more preferably 0 or 1, and most preferably 0.

As the lower alkyl group for R¹′ and R²′, the same lower alkyl groups as those described above for R¹ can be used, although a methyl group or ethyl group is preferable, and a methyl group is particularly desirable.

In the present invention, it is preferable that at least one of R¹′ and R²′ be a hydrogen atom. That is, it is preferable that the acid dissociable, dissolution inhibiting group (p1) is a group represented by general formula (p1-1) shown below.

In the formula, R¹′, n and Y are the same as defined above.

As the lower alkyl group for Y, the same as the lower alkyl groups for R¹ can be used.

As the aliphatic cyclic group for Y, any of the aliphatic monocyclic/polycyclic groups which have been proposed for conventional ArF resists and the like can be appropriately selected for use. For example, the same groups described above in connection with the “aliphatic cyclic group” can be used.

Further, as the acetal-type, acid dissociable, dissolution inhibiting group, groups represented by general formula (p2) shown below can also be used.

In the formula, R¹⁷ and R¹⁸ each independently represent a linear or branched alkyl group or a hydrogen atom; and R¹⁹ represents a linear, branched or cyclic alkyl group; or R¹⁷ and R¹⁹ each independently represents a linear or branched alkylene group, and the terminal of R¹⁷ is bonded to the terminal of R¹⁹ to form a ring.

The alkyl group for R¹⁷ and R¹⁸ preferably has 1 to 15 carbon atoms, and may be either linear or branched. As the alkyl group, an ethyl group or a methyl group is preferable, and a methyl group is most preferable.

It is particularly desirable that either one of R¹⁷ and R¹⁸ be a hydrogen atom, and the other be a methyl group.

R¹⁹ represents a linear, branched or cyclic alkyl group which preferably has 1 to 15 carbon atoms, and may be any of linear, branched or cyclic.

When R¹⁹ represents a linear or branched alkyl group, it is preferably an alkyl group of 1 to 5 carbon atoms, more preferably an ethyl group or methyl group, and most preferably an ethyl group.

When R¹⁹ represents a cycloalkyl group, it preferably has 4 to 15 carbon atoms, more preferably 4 to 12 carbon atoms, and most preferably 5 to 10 carbon atoms. As examples of the cycloalkyl group, groups in which one or more hydrogen atoms have been removed from a monocycloalkane or a polycycloalkane such as a bicycloalkane, tricycloalkane or tetracycloalkane, which may or may not be substituted with a fluorine atom or a fluorinated alkyl group, may be used. Specific examples include groups in which one or more hydrogen atoms have been removed from a monocycloalkane such as cyclopentane and cyclohexane; and groups in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane or tetracyclododecane. Among these, a group in which one or more hydrogen atoms have been removed from adamantane is preferable.

In general formula (p2) above, R¹⁷ and R¹⁹ may each independently represent a linear or branched alkylene group (preferably an alkylene group of 1 to 5 carbon atoms), and the terminal of R¹⁹ may be bonded to the terminal of R¹⁷.

In such a case, a cyclic group is formed by R¹⁷, R¹⁹, the oxygen atom having R¹⁹ bonded thereto, and the carbon atom having the oxygen atom and R¹⁷ bonded thereto. Such a cyclic group is preferably a 4 to 7-membered ring, and more preferably a 4 to 6-membered ring. Specific examples of the cyclic group include tetrahydropyranyl group and tetrahydrofuranyl group.

Specific examples of acetal-type acid dissociable, dissolution inhibiting groups include groups represented by formulas (p3-1) to (p3-12) shown below.

In the formulas above, R¹³ represents a hydrogen atom or a methyl group; and g is the same as defined above.

Specific examples of the structural unit (a1) include a structural unit represented by general formula (a1-0-1) shown below and a structural unit represented by general formula (a1-0-2) shown below.

In the formulas, R represents a hydrogen atom, a lower alkyl group or a halogenated lower alkyl group; X¹ represents an acid dissociable, dissolution inhibiting group; Y² represents a divalent linking group; and X² represents an acid dissociable, dissolution inhibiting group.

In general formula (a1-0-1), R is the same as defined for R¹ in formula (a0-1).

X¹ is not particularly limited as long as it is an acid dissociable, dissolution inhibiting group. Examples thereof include the aforementioned tertiary alkyl ester-type acid dissociable, dissolution inhibiting groups and acetal-type acid dissociable, dissolution inhibiting groups, and tertiary alkyl ester-type acid dissociable, dissolution inhibiting groups are preferable.

In general formula (a1-0-2), R is the same as defined above.

X² is the same as defined for X¹ in general formula (a1-0-1).

As examples of the divalent linking group for Y², the same groups as those described above for R² in formula (a0-1) can be given.

As Y², the aforementioned alkylene group, a divalent aliphatic cyclic group or a divalent linking group containing a hetero atom is preferable. Among these, a divalent linking group containing a hetero atom is preferable, and a linear group containing an oxygen atom as a heteratom, e.g., a group containing an ester bond is particularly desirable.

More specifically, a group represented by the aforementioned formula -A-O—B— or -A—C(═O)—O—B— is preferable, and a group represented by the formula —(CH₂)_(a)—C(═O)—O—(CH₂)_(b)— is particularly desirable.

a represents an integer of 1 to 5, preferably 1 or 2, and most preferably 1.

b represents an integer of 1 to 5, preferably 1 or 2, and most preferably 1.

Specific examples of the structural unit (a1) include structural units represented by general formulas (a1-1) to (a1-4) shown below.

In the formulas, X′ represents a tertiary alkyl ester-type acid dissociable, dissolution inhibiting group; Y represents a lower alkyl group of 1 to 5 carbon atoms or an aliphatic cyclic group; n represents an integer of 0 to 3; Y² represents a divalent linking group; R is the same as defined above; and each of R¹′ and R²′ independently represents a hydrogen atom or a lower alkyl group of 1 to 5 carbon atoms.

Examples of the tertiary alkyl ester-type acid dissociable, dissolution inhibiting group for X′ include the same tertiary alkyl ester-type acid dissociable, dissolution inhibiting groups as those described above for X¹.

As R¹′, R²′, n and Y are respectively the same as defined for R¹′, R²′, n and Y in general formula (p1) described above in connection with the “acetal-type acid dissociable, dissolution inhibiting group”.

As examples of Y², the same groups as those described above for Y² in general formula (a1-0-2) can be given.

Specific examples of structural units represented by general formula (a1-1) to (a1-4) are shown below.

In the formulas shown below, R^(α) represents a hydrogen atom, a methyl group or a trifluoromethyl group.

As the structural unit (a1), one type of structural unit may be used, or two or more types may be used in combination.

In the present invention, in terms of achieving excellent lithography properties with respect to resolution, the shape of resist pattern and the like, it is particularly desirable that the structural unit (a1) includes at least one structural unit selected from the group consisting of a structural unit represented by general formula (a1-0-11) shown below, a structural unit represented by general formula (a1-0-12) shown below and a structural unit represented by general formula (a1-0-2) shown below.

In the formulas, R represents a hydrogen atom, a lower alkyl group or a halogenated lower alkyl group; R²¹ represents an alkyl group; R²² represents a group which forms an aliphatic monocyclic group with the carbon atoms to which R²² is bonded; R²³ represents a branched alkyl group; R²⁴ represents a group which forms an aliphatic polycyclic group with the carbon atoms to which R²⁴ is bonded; Y² represents a divalent linking group; and X² represents an acid dissociable, dissolution inhibiting group.

In the formulas, R, Y² and X² are the same as defined above.

In general formula (a1-0-11), as the alkyl group for R²¹, the same alkyl groups as those described above for R¹⁴ in formulas (1-1) to (1-9) can be used, preferably a methyl group or an ethyl group, and most preferably an ethyl group.

As the aliphatic monocyclic group formed by R²² and the carbon atoms to which R²² is bonded, the same aliphatic cyclic groups as those described above for the aforementioned tertiary alkyl ester-type acid dissociable, dissolution inhibiting group and which are monocyclic can be used. Specific examples include groups in which one or more hydrogen atoms have been removed from a monocycloalkane. The monocycloalkane is preferably a 3- to 11-membered ring, more preferably a 3- to 8-membered ring, still more preferably a 4- to 6-membered ring, and most preferably a 5- or 6-membered ring.

The monocycloalkane may or may not have part of the carbon atoms constituting the ring replaced with an ethereal oxygen atom (—O—).

Further, the monocycloalkane may have a substituent such as a lower alkyl group, a fluorine atom or a fluorinated alkyl group.

As an examples of R²² constituting such an aliphatic cyclic group, an alkylene group which may have an ethereal oxygen atom (—O—) interposed between the carbon atoms can be given.

Specific examples of structural units represented by general formula (a1-0-11) include structural units represented by the aforementioned formulas (a1-1-16) to (a1-1-23). Among these, a structural unit represented by general formula (a1-1-02) shown below which includes the structural units represented by the aforementioned formulas (a1-1-16), (a1-1-17) and (a1-1-20) to (a1-1-23) is preferable. Further, a structural unit represented by general formula (a1-1-02′) shown below is also preferable.

In the formulas shown below, h is preferably 1 or 2, and most preferably 2.

In the formulas, R and R²¹ are the same as defined above; and h represents an integer of 1 to 3.

In general formula (a1-0-12), as the branched alkyl group for R²³, the same alkyl groups as those described above for R¹⁴ which are branched can be used, and an isopropyl group is particularly desirable.

As the aliphatic polycyclic group formed by R²⁴ and the carbon atoms to which R²⁴ is bonded, the same aliphatic cyclic groups as those described above for the aforementioned tertiary alkyl ester-type acid dissociable, dissolution inhibiting group and which are polycyclic can be used.

Specific examples of structural units represented by general formula (a1-0-12) include structural units represented by the aforementioned formulas (a1-1-26) to (a1-1-31).

Examples of structural units represented by general formula (a1-0-2) include structural units represented by the aforementioned formulas (a1-3) and (a1-4).

As a structural unit represented by general formula (a1-0-2), those in which Y² is a group represented by the aforementioned formula -A-O—B— or -A-C(═O)—O—B— is particularly desirable.

Preferable examples of such structural units include a structural unit represented by general formula (a1-3-01) shown below, a structural unit represented by general formula (a1-3-02) shown below, and a structural unit represented by general formula (a1-3-03) shown below.

In the formula, R and R″ are the same as defined above; R¹³ represents a hydrogen atom or a methyl group; and a represents an integer of 1 to 10.

In the formula, R and R¹⁴ are the same as defined above; R¹³ represents a hydrogen atom or a methyl group; a represents an integer of 1 to 10; and n′ represents an integer of 0 to 3.

In the formula, R is as defined above; each of Y²′ and Y²″ independently represents a divalent linking group; X′ represents an acid dissociable, dissolution inhibiting group; and n represents an integer of 1 to 3.

In general formulas (a1-3-01) and (a1-3-02), R¹³ is preferably a hydrogen atom.

a is preferably an integer of 1 to 8, more preferably 1 to 5, and most preferably 1 or 2.

n′ is preferably 1 or 2, and most preferably 2.

Specific examples of structural units represented by general formula (a1-3-01) include structural units represented by the aforementioned formulas (a1-3-25) and (a1-3-26).

Specific examples of structural units represented by general formula (a1-3-02) include structural units represented by the aforementioned formulas (a1-3-27) and (a1-3-28).

In general formula (a1-3-03), as the divalent linking group for Y²′ and Y²″, the same groups as those described above for Y² in general formula (a1-3) can be used.

As Y²′, a divalent hydrocarbon group which may have a substituent is preferable, a linear aliphatic hydrocarbon group is more preferable, and a linear alkylene group is still more preferable. Among linear alkylene groups, a linear alkylene group of 1 to 5 carbon atoms is preferable, and a methylene group or an ethylene group is particularly desirable.

As Y²″, a divalent hydrocarbon group which may have a substituent is preferable, a linear aliphatic hydrocarbon group is more preferable, and a linear alkylene group is still more preferable. Among linear alkylene groups, a linear alkylene group of 1 to 5 carbon atoms is preferable, and a methylene group or an ethylene group is particularly desirable.

As the acid dissociable, dissolution inhibiting group for X′, the same groups as those described above can be used. X′ is preferably a tertiary alkyl ester-type acid dissociable, dissolution inhibiting group, more preferably the aforementioned group (i) which has a tertiary carbon atom on the ring structure of a monovalent aliphatic cyclic group. Among the aforementioned groups (i), a group represented by general formula (1-1) above is preferable.

n represents an integer of 0 to 3, preferably an integer of 0 to 2, more preferably 0 or 1, and most preferably 1.

As the structural unit represented by general formula (a1-3-03), a structural unit represented by general formula (a1-3-03-1) or (a1-3-03-2) shown below is preferable. Among these, a structural unit represented by general formula (a1-3-03-1) is preferable, and a structural unit represented by the aforementioned formula (a1-3-29) or (a1-3-30) is particularly desirable.

In the formulas, R and R¹⁴ are the same as defined above; R²⁰ represents a hydrogen atom or a methyl group; a represents an integer of 1 to 10; b represents an integer of 1 to 10; and t represents an integer of 0 to 3.

a is preferably an integer of 1 to 5, and most preferably 1 or 2.

b is preferably an integer of 1 to 5, and most preferably 1 or 2.

t is preferably an integer of 1 to 3, and most preferably 1 or 2.

In the present invention, it is particularly desirable to include at least two types of structural units as the structural unit (a1).

In such a case, it is preferable that at least one of the at least two structural units is a structural unit selected from the group consisting of a structural unit represented by general formula (a1-0-11), a structural unit represented by general formula (a1-0-12) and a structural unit represented by general formula (a1-0-2).

The structural unit (a1) including at least two types of structural units may consist of structural units selected from the group consisting of a structural unit represented by general formula (a1-0-11), a structural unit represented by general formula (a1-0-12) and a structural unit represented by general formula (a1-0-2). Alternatively, the structural unit (a1) may be a combination of at least one structural unit selected from the aforementioned group and a structural unit which does not fall under the category of the aforementioned group.

As examples of the structural unit which can be used in combination with at least one structural unit selected from the group consisting of a structural unit represented by general formula (a1-0-11), a structural unit represented by general formula (a1-0-12) and a structural unit represented by general formula (a1-0-2) and does not fall under the category of the aforementioned group, a structural unit represented by general formula (a1-1-10) shown below which includes the structural units represented by the aforementioned (a1-1-1), (a1-1-2), (a1-1-7) to (a1-1-15) described above as specific examples of structural units represented by general formula (a1-1), structural units represented by general formula (a1-2) and structural units represented by general formula (a1-4) can be given.

As a structural unit represented by general formula (a1-1-10), a structural unit represented by general formula (a1-1-101) shown below which includes the aforementioned formulas (a1-1-1) and (a1-1-2) is particularly desirable.

In the formulas, R is the same as defined above; each of R²⁵ and R¹¹ independently represents a linear alkyl group of 1 to 5 carbon atoms; and R²⁴ is the same as defined above.

In the component (A1) or (A1′), the amount of the structural unit (a1) based on the combined total of all structural units constituting the component (A1) or (A1′) is preferably 10 to 80 mol %, more preferably 20 to 70 mol %, and still more preferably 25 to 50 mol %. By ensuring that the amount of the structural unit (a1) is at least as large as the lower limit of the above-mentioned range, a pattern can be easily formed using a resist composition prepared from the component (A1). On the other hand, by ensuring that the amount of the structural unit (a1) is no more than the upper limit of the above-mentioned range, a good balance can be achieved with the other structural units.

(Structural Unit (a2))

The structural unit (a2) is a structural unit derived from an acrylate ester containing a lactone-containing cyclic group which does not fall under the category of the aforementioned structural units (a0) and (a1).

The term “lactone-containing cyclic group” refers to a cyclic group including one ring containing a —O—C(O)— structure (lactone ring). The term “lactone ring” refers to a single ring containing a —O—C(O)— structure, and this ring is counted as the first ring. A lactone-containing cyclic group in which the only ring structure is the lactone ring is referred to as a monocyclic group, and groups containing other ring structures are described as polycyclic groups regardless of the structure of the other rings.

When the component (A1) or (A1′) is used for forming a resist film, the lactone-containing cyclic group of the structural unit (a2) is effective in improving the adhesion between the resist film and the substrate, and increasing the compatibility with the developing solution containing water.

As the structural unit (a2), there is no particular limitation, and an arbitrary structural unit may be used.

Specific examples of lactone-containing monocyclic groups include a group in which one hydrogen atom has been removed from a 4- to 6-membered lactone ring, such as a group in which one hydrogen atom has been removed from β-propionolatone, a group in which one hydrogen atom has been removed from γ-butyrolactone, and a group in which one hydrogen atom has been removed from δ-valerolactone. Further, specific examples of lactone-containing polycyclic groups include groups in which one hydrogen atom has been removed from a lactone ring-containing bicycloalkane, tricycloalkane or tetracycloalkane.

More specifically, examples of the structural unit (a2) include structural units represented by general formulas (a2-1) to (a2-5) shown below.

In the formula, R, R′ and A″ are the same as defined above; R²⁹ represents a single bond or a divalent linking group; s″ represents an integer of 0 to 2; and m represents 0 or 1.

R²⁹ represents a single bond or a divalent linking group Examples of divalent linking groups include the same divalent linking groups as those described above for R². Among these, an alkylene group, an ester bond (—C(═O)—O—) or a combination thereof is preferable. The alkylene group as a divalent linking group for R²⁹ is preferably a linear or branched alkylene group. Specific examples include the same linear alkylene groups and branched alkylene groups as those described above for R².

S″ is preferably 1 or 2.

Specific examples of structural units represented by general formulas (a2-1) to (a2-5) are shown below. In the formulas shown below, R^(α) represents a hydrogen atom, a methyl group or a trifluoromethyl group.

In the component (A1) or (A1′), as the structural unit (a2), one type of structural unit may be used, or two or more types may be used in combination.

In the present invention, when the component (A) includes the component (A1), it is particularly desirable that the component (A1) contain, as a structural unit (a2), at least one structural unit selected from the group consisting of a structural unit represented by general formula (a2-1) and a structural unit represented by general formula (a2-2).

When the component (A) includes the component (A1), in terms of improving the adhesion between a substrate and a resist film formed using a positive resist composition containing the component (A1) and increasing the compatibility with a developing solution, the amount of the structural unit (a2) within the component (A1), based on the combined total of all structural units constituting the component (A1) is preferably 1 to 50 mol %, more preferably 5 to 50 mol %, and still more preferably 10 to 45 mol %.

Further, in terms of achieving excellent lithography properties, the amount of the structural unit (a0) and the structural unit (a2) (the amount of the structural unit (a0) when the component (A1) contains no structural unit (a2)) within the component (A1), based on the combined total of all structural units constituting the component (A1) is preferably 5 to 70 mol %, more preferably 1 to 70 mol %, still more preferably 10 to 65 mol %, and most preferably 20 to 65 mol %. By ensuring the above-mentioned range, MEF, CDU and the pattern shape can be further improved.

When the component (A1) contains both of the structural unit (a0) and the structural unit (a2), the amount of the structural unit (a0) within the component (A1), based on the combined total of all structural units constituting the component (A1) is preferably 1 to 40 mol %, more preferably 10 to 35 mol %, and most preferably 15 to 30 mol %; and the amount of the structural unit (a2) within the component (A1), based on the combined total of all structural units constituting the component (A1) is preferably 1 to 45 mol %, more preferably 10 to 45 mol %, and most preferably 20 to 45 mol %.

On the other hand, when the component (A) includes the component (A1′), in terms of improving the adhesion between a substrate and a resist film formed using a positive resist composition containing the component (A1′) and increasing the compatibility with a developing solution, the amount of the structural unit (a2) within the component (A1′), based on the combined total of all structural units constituting the component (A1′) is preferably 5 to 70 mol %, more preferably 10 to 65 mol %, still more preferably 20 to 65 mol %, and most preferably 20 to 45 mol %. By ensuring the above-mentioned range, MEF, CDU and the pattern shape can be further improved.

Further, in terms of achieving excellent lithography properties, the amount of the structural unit (a0) and the structural unit (a2) within the component (A1′), based on the combined total of all structural units constituting the component (A1′) is preferably 5 to 70 mol %, more preferably 1 to 70 mol %, still more preferably 10 to 65 mol %, and most preferably 20 to 65 mol %. By ensuring the above-mentioned range, MEF, CDU and the pattern shape can be further improved.

The component (A1′) includes an acid dissociable, dissolution inhibiting group within the structure thereof.

The acid dissociable, dissolution inhibiting group is a group having an alkali dissolution-inhibiting effect that renders the entire component (A1′) insoluble in an alkali developing solution prior to dissociation, and is dissociated from the component (A1′) by the action of acid generated from the component (B) upon exposure. Therefore, when the acid dissociable, dissolution inhibiting group is dissociated from the component (A1′), the solubility of the entire component (A1′) in an alkali developing solution is increased.

The acid dissociable, dissolution inhibiting group can be incorporated into the component (A1′) by using a structural unit (a0) and/or a structural unit (a2) that contains an acid dissociable, dissolution inhibiting group within the structure thereof, or by using a structural unit other than the structural units (a0) and (a2) that contains an acid dissociable, dissolution inhibiting group.

For example, the structural units represented by formulas (a2-1-5) to (a2-1-7), (a2-2-10) and (a2-2-11) described above for the structural unit (a2) contain a lactone-containing cyclic group that functions as an acid dissociable, dissolution inhibiting group.

Further, among the structural units described above for the structural unit (a0), with respect to a structural unit in which a tertiary carbon atom is bonded to the terminal oxygen atom of the carbonyloxy group (—C(O)—O—) bonded to the cyclic group in formula (a0-1) (e.g., a structural unit in which R′ represents an alkyl group, and the cyclic group in formula (a0-1) represents an acid dissociable, dissolution inhibiting group, as in the case of the structural unit (a2) described above), the cyclic group also functions as an acid dissociable, dissolution inhibiting group. Furthermore, in a structural unit (a0) in which R² has an acid dissociable portion within the structure thereof, the portion from the acid dissociable portion to the terminal functions as an acid dissociable, dissolution inhibiting group.

When such a structural unit containing an acid dissociable, dissolution inhibiting group-equivalent group/portion within the structure thereof is used as the structural unit (a0) and/or structural unit (a2), the component (A1′) may consist of the structural units (a0) and (a2), or may further contain an optional structural unit (e.g., the aforementioned structural unit (a1), or the structural unit (a3) or (a4) described later).

On the other hand, when a structural unit containing no acid dissociable, dissolution inhibiting group-equivalent group/portion within the structure thereof is used as the structural unit (a0) and/or structural unit (a2), it is necessary that the component (A1′) contain a structural unit having an acid dissociable, dissolution inhibiting group (e.g., the aforementioned structural unit (a1), the below-described structural unit (a3), the below-described structural unit (A4), or the like) in addition to the structural units (a0) and (a2).

In the present invention, as a structural unit having an acid dissociable, dissolution inhibiting group, it is preferable to contain the aforementioned structural unit (a1).

(Structural Unit (a3))

The structural unit (a3) is a structural unit derived from an acrylate ester containing a polar group-containing aliphatic hydrocarbon group.

When the component (A1) or (A1′) includes the structural unit (a3), the hydrophilicity of the component (A) is improved, and hence, the compatibility of the component (A) with the developing solution is improved. As a result, the alkali solubility of the exposed portions improves, which contributes to favorable improvements in the resolution.

Examples of the polar group include a hydroxyl group, a cyano group, a carboxyl group, or a fluorinated alcohol group (a hydroxyalkyl group in which part of the hydrogen atoms of the alkyl group have been substituted with fluorine atoms), although a hydroxyl group is particularly desirable.

Examples of the aliphatic hydrocarbon group include linear or branched hydrocarbon groups (and preferably alkylene groups) of 1 to 10 carbon atoms, and polycyclic aliphatic hydrocarbon groups (polycyclic groups). These polycyclic groups can be selected appropriately from the multitude of groups that have been proposed for the resins of resist compositions designed for use with ArF excimer lasers. The polycyclic group preferably has 7 to 30 carbon atoms.

Of the various possibilities, structural units derived from an acrylate ester that include an aliphatic polycyclic group that contains a hydroxyl group, a cyano group, a carboxyl group or a fluorinated alcohol group are particularly desirable. Examples of polycyclic groups include groups in which two or more hydrogen atoms have been removed from a bicycloalkane, tricycloalkane, tetracycloalkane or the like. Specific examples include groups in which two or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane or tetracyclododecane. Of these polycyclic groups, groups in which two or more hydrogen atoms have been removed from adamantane, norbornane or tetracyclododecane are preferred industrially.

When the aliphatic hydrocarbon group within the polar group-containing aliphatic hydrocarbon group is a linear or branched hydrocarbon group of 1 to 10 carbon atoms, the structural unit (a3) is preferably a structural unit derived from a hydroxyethyl ester of acrylic acid. On the other hand, when the hydrocarbon group is a polycyclic group, structural units represented by formulas (a3-1), (a3-2) and (a3-3) shown below are preferable.

In the formulas, R is as defined above; j is an integer of 1 to 3; k is an integer of 1 to 3; t′ is an integer of 1 to 3; 1 is an integer of 1 to 5; and s is an integer of 1 to 3.

In formula (a3-1), j is preferably 1 or 2, and more preferably 1. When j is 2, it is preferable that the hydroxyl groups be bonded to the 3rd and 5th positions of the adamantyl group. When j is 1, it is preferable that the hydroxyl group be bonded to the 3rd position of the adamantyl group.

In formula (a3-2), k is preferably 1. The cyano group is preferably bonded to the 5th or 6th position of the norbornyl group.

In formula (a3-3), t′ is preferably 1. 1 is preferably 1. s is preferably 1. Further, in formula (a3-3), it is preferable that a 2-norbornyl group or 3-norbornyl group be bonded to the terminal of the carboxy group of the acrylic acid. The fluorinated alkyl alcohol is preferably bonded to the 5th or 6th position of the norbornyl group.

As the structural unit (a3), one type of structural unit may be used, or two or more types may be used in combination.

The amount of the structural unit (a3) based on the combined total of all structural units constituting the component (A1) or (A1′) is preferably 5 to 50 mol %, more preferably 5 to 40 mol %, still more preferably 5 to 25 mol %, and most preferably 5 to 15 mol %.

(Other Structural Units)

The component (A1) or (A1′) may also have a structural unit (a4) which is other than the above-mentioned structural units (a0) to (a3), as long as the effects of the present invention are not impaired.

As the structural unit (a4), any other structural unit which cannot be classified as one of the above structural units (a0) to (a3) can be used without any particular limitation, and any of the multitude of conventional structural units used within resist resins for ArF excimer lasers or KrF excimer lasers (and particularly for ArF excimer lasers) can be used.

As the structural unit (a4), a structural unit which contains a non-acid-dissociable aliphatic polycyclic group, and is also derived from an acrylate ester is preferable. Examples of this polycyclic group include the same groups as those described above in connection with the aforementioned structural unit (a1), and any of the multitude of conventional polycyclic groups used within the resin component of resist compositions for ArF excimer lasers or KrF excimer lasers (and particularly for ArF excimer lasers) can be used.

In consideration of industrial availability and the like, at least one polycyclic group selected from amongst a tricyclodecanyl group, adamantyl group, tetracyclododecanyl group, isobornyl group, and norbornyl group is particularly desirable. These polycyclic groups may be substituted with a linear or branched alkyl group of 1 to 5 carbon atoms.

Specific examples of the structural unit (a4) include units with structures represented by general formulas (a4-1) to (a4-5) shown below.

In the formulas, R is the same as defined above.

When the structural unit (a4) is included in the component (A1) or (A1′), the amount of the structural unit (a4) based on the combined total of all the structural units that constitute the component (A1) or (A1′) is preferably within the range from 1 to 30 mol %, and more preferably from 10 to 20 mol %.

The component (A1) is preferably a copolymer containing the structural units (a0) and (a1). Examples of such copolymers include a copolymer consisting of the structural units (a0) and (a1), a copolymer consisting of the structural units (a0), (a1) and (a3), a copolymer consisting of the structural units (a0), (a1) and (a2), and a copolymer consisting of the structural units (a0), (a1), (a2) and (a3).

The component (A1′) is preferably a copolymer containing the structural units (a0) and (a2), and more preferably a copolymer containing the structural units (a0), (a1) and (a2). Examples of such copolymers include a copolymer consisting of the structural units (a0) and (a2), a copolymer consisting of the structural units (a0), (a1) and (a2), and a copolymer consisting of the structural units (a0), (a1), (a2) and (a3). However, in the case of a copolymer consisting of the structural units (a0) and (a2), it is necessary that either or both of the structural units (a0) and (a2) contain an acid dissociable, dissolution inhibiting group.

In the present invention, it is particularly desirable that such a copolymer contains, as the structural unit (a1), at least one member selected from the group consisting of a structural unit represented by general formula (a1-0-11), a structural unit represented by general formula (a1-0-12), and a structural unit represented by general formula (a1-0-2).

Further, as described above, such a copolymer preferably contains at least two types of structural units as the structural unit (a1), and it is particularly desirable that at least one of the at least two structural units is selected from the group consisting of a structural unit represented by general formula (a1-0-11), a structural unit represented by general formula (a1-0-12), and a structural unit represented by general formula (a1-0-2).

The weight average molecular weight (Mw) (the polystyrene equivalent value determined by gel permeation chromatography) of the component (A1) or (A1′) is not particularly limited, but is preferably 2,000 to 50,000, more preferably 3,000 to 30,000, and most preferably 5,000 to 20,000. By ensuring that the weight average molecular weight is no more than the upper limit of the above-mentioned range, the polymeric compound (A1) exhibits satisfactory solubility in a resist solvent when used as a resist. On the other hand, by ensuring that the weight average molecular weight is at least as large as the lower limit of the above-mentioned range, dry etching resistance and cross-sectional shape of the resist pattern becomes satisfactory.

Further, the dispersity (Mw/Mn) is preferably 1.0 to 5.0, more preferably 1.0 to 3.0, and most preferably 1.2 to 2.5. Here, Mn is the number average molecular weight.

In the component (A), as the component (A1) or (A1′), one type may be used, or two or more types of compounds may be used in combination.

In the component (A), the amount of the component (A1) or (A1′) based on the total weight of the component (A) is preferably 25% by weight or more, more preferably 50% by weight or more, still more preferably 75% by weight or more, and may be even 100% by weight. When the amount of the component (A1) is 25% by weight or more, various lithography properties are improved.

The component (A1) or (A1′) can be obtained, for example, by a conventional radical polymerization or the like of the monomers corresponding with each of the structural units, using a radical polymerization initiator such as azobisisobutyronitrile (AIBN).

Furthermore, in the component (A1) or (A1′), by using a chain transfer agent such as HS—CH₂—CH₂—CH₂—C(CF₃)₂—OH, a —C(CF₃)₂—OH group can be introduced at the terminals of the component (A1) or (A1′). Such a copolymer having introduced a hydroxyalkyl group in which some of the hydrogen atoms of the alkyl group are substituted with fluorine atoms is effective in reducing developing defects and LER (line edge roughness: unevenness of the side walls of a line pattern).

As the monomers for deriving the corresponding structural units, commercially available monomers may be used, or the monomers may be synthesized by a conventional method.

For example, as a monomer for deriving the structural unit (a0), a compound (I) represented by general formula (I) shown below can be used.

In general formula (I), R¹, R², R′ and A″ are the same as defined above.

The method for producing the compound (I) is not particularly limited, and the compound (I) can be produced by a conventional method.

For example, in the presence of a base, a compound (X-2) represented by general formula (X-2) shown below is added to a solution obtained by dissolving a compound (X-1) represented by general formula (X-1) shown below in a reaction solvent, and a reaction is effected to thereby obtain a compound (I).

Examples of the base include inorganic bases such as sodium hydride, K₂CO₃ and Cs₂CO₃; and organic bases such as triethylamine, 4-dimethylaminopyridine (DMAP) and pyridine. Examples of condensing agents include carbodiimide reagents such as ethyldiisopropylaminocarbodiimide hydrochloride (EDCI), dicyclohexylcarboxyimide (DCC), diisopropylcarbodiimide and carbodiimidazole; tetraethyl pyrophosphate; and benzotriazole-N-hydroxytrisdimethylaminophosphonium hexafluorophosphide (Bop reagent).

If desired, an acid may be used. As the acid, any acid generally used for dehydration/condensation may be used. Specific examples include inorganic acids such as hydrochloric acid, sulfuric acid and phosphoric acid; and organic acids such as methanesulfonic acid, trifluoromethanesulfonic acid, benzenesulfonic acid and p-toluenesulfonic acid. These acids can be used individually, or in a combination of two or more.

In general formula (I), R¹, R², R′ and A″ are the same as defined above.

In the resist composition of the present invention, the component (A) may contain “a base component which exhibits increased solubility in an alkali developing solution under action of acid” other than the component (A1) and (A1′) (hereafter, referred to as “component (A2)”).

The component (A2) is not particularly limited, and any of the multitude of conventional base components used within chemically amplified resist compositions (e.g., base resins used within chemically amplified resist compositions for ArF excimer lasers or KrF excimer lasers, preferably ArF excimer lasers) can be used. For example, as a base resin for ArF excimer laser, a base resin having the aforementioned structural unit (a1) as an essential component, and optionally the aforementioned structural units (a2) to (a4) can be used.

As the component (A2), one type of resin may be used, or two or more types of resins may be used in combination.

In the resist composition of the present invention, the amount of the component (A) can be appropriately adjusted depending on the thickness of the resist film to be formed, and the like.

<Component (B)>

As the component (B), there is no particular limitation, and any of the known acid generators used in conventional chemically amplified resist compositions can be used. Examples of these acid generators are numerous, and include onium salt acid generators such as iodonium salts and sulfonium salts; oxime sulfonate acid generators; diazomethane acid generators such as bisalkyl or bisaryl sulfonyl diazomethanes and poly(bis-sulfonyl)diazomethanes; nitrobenzylsulfonate acid generators; iminosulfonate acid generators; and disulfone acid generators.

As an onium salt acid generator, a compound represented by general formula (b-1) or (b-2) shown below can be used.

In the formulas above, R″ to R³″, R⁵″ and R⁶″ each independently represent an aryl group or alkyl group, wherein two of R″ to R³″ may be bonded to each other to form a ring with the sulfur atom; and R⁴″ represents an alkyl group, a halogenated alkyl group, an aryl group or an alkenyl group which may have a substituent, with the provision that at least one of R¹″ to R³″ represents an aryl group, and at least one of R⁵″ and R⁶″ represents an aryl group.

In formula (b-1), R¹″ to R³″ each independently represents an aryl group or an alkyl group. In formula (b-1), two of R¹″ to R³″ may be bonded to each other to form a ring with the sulfur atom.

Further, among R¹″ to R³″, at least one group represents an aryl group. Among R¹″ to R³″, two or more groups are preferably aryl groups, and it is particularly desirable that all of R¹″ to R³″ are aryl groups.

The aryl group for R¹″ to R³″ is not particularly limited. For example, an aryl group having 6 to 20 carbon atoms may be used in which part or all of the hydrogen atoms of the aryl group may or may not be substituted with alkyl groups, alkoxy groups, halogen atoms or hydroxyl groups.

The aryl group is preferably an aryl group having 6 to 10 carbon atoms because it can be synthesized at a low cost. Specific examples thereof include a phenyl group and a naphthyl group.

The alkyl group, with which hydrogen atoms of the aryl group may be substituted, is preferably an alkyl group having 1 to 5 carbon atoms, and most preferably a methyl group, an ethyl group, a propyl group, an n-butyl group, or a tert-butyl group.

The alkoxy group, with which hydrogen atoms of the aryl group may be substituted, is preferably an alkoxy group having 1 to 5 carbon atoms, more preferably a methoxy group, an ethoxy group, an n-propoxy group, an iso-propoxy group, an n-butoxy group or a tert-butoxy group, and most preferably a methoxy group or an ethoxy group.

The halogen atom, with which hydrogen atoms of the aryl group may be substituted, is preferably a fluorine atom.

The alkyl group for R¹″ to R³″ is not particularly limited and includes, for example, a linear, branched or cyclic alkyl group having 1 to 10 carbon atoms. In terms of achieving excellent resolution, the alkyl group preferably has 1 to 5 carbon atoms.

Specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an n-pentyl group, a cyclopentyl group, a hexyl group, a cyclohexyl group, a nonyl group, and a decanyl group, and a methyl group is most preferable because it is excellent in resolution and can be synthesized at a low cost.

When two of R¹″ to R³″ in formula (b-1) are bonded to each other to form a ring with the sulfur atom, it is preferable that the two of R¹″ to R³″ form a 3 to 10-membered ring including the sulfur atom, and it is particularly desirable that the two of R¹″ to R³″ form a 5 to 7-membered ring including the sulfur atom.

When two of R¹″ to R³″ in formula (b-1) are bonded to each other to form a ring with the sulfur atom, the remaining one of R¹″ to R³″ is preferably an aryl group. As examples of the aryl group, the same as the above-mentioned aryl groups for R¹″ to R³″ can be given.

As preferable examples of the cation moiety for the compound represented by general formula (b-1), those represented by formulas (I-1-1) to (I-1-13), (I-2-1) and (I-2-2) shown below can be given. Among these, a cation moiety having a triphenylmethane skeleton, such as a cation moiety represented by any one of formulas (I-1-1) to (I-1-13) shown below is particularly desirable. Further, a group in which part or all of the phenyl groups within the cation moiety having a triphenylmethane skeleton have been replaced with a naphthyl group which may have a substituent can also be given as a preferable example.

In formulas (I-2-1) and (I-2-2), each of R⁹ and R¹⁰ independently represents a phenyl group or naphthyl group which may have a substituent, an alkyl group of 1 to 5 carbon atoms, an alkoxy group or a hydroxy group.

u is an integer of 1 to 3, and most preferably 1 or 2.

R⁴″ represents an alkyl group, a halogenated alkyl group, an aryl group or an alkenyl group which may have a substituent.

The alkyl group for R⁴″ may be any of linear, branched or cyclic.

The linear or branched alkyl group preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 4 carbon atoms.

The cyclic alkyl group preferably has 4 to 15 carbon atoms, more preferably 4 to 10 carbon atoms, and most preferably 6 to 10 carbon atoms.

As an example of the halogenated alkyl group for R⁴″, a group in which part of or all of the hydrogen atoms of the aforementioned linear, branched or cyclic alkyl group have been substituted with halogen atoms can be given. Examples of the aforementioned halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, and a fluorine atom is preferable.

In the halogenated alkyl group, the percentage of the number of halogen atoms based on the total number of halogen atoms and hydrogen atoms (halogenation ratio (%)) is preferably 10 to 100%, more preferably 50 to 100%, and most preferably 100%. Higher halogenation ratio is preferable because the acid strength increases.

The aryl group for R⁴″ is preferably an aryl group of 6 to 20 carbon atoms.

The alkenyl group for R⁴″ is preferably an alkenyl group of 2 to 10 carbon atoms.

With respect to R⁴″, the expression “may have a substituent” means that part of or all of the hydrogen atoms within the aforementioned linear, branched or cyclic alkyl group, halogenated alkyl group, aryl group or alkenyl group may be substituted with substituents (atoms other than hydrogen atoms, or groups).

R⁴″ may have one substituent, or two or more substituents.

Examples of the substituent include a halogen atom, a hetero atom, an alkyl group which may have a substituent, and a group represented by the formula X-Q¹- (in the formula, Q¹ represents a divalent linking group containing an oxygen atom; and X represents a hydrocarbon group of 3 to 30 carbon atoms which may have a substituent).

Examples of the halogen atom as the substituent for R⁴″ include the same halogen atoms as those described above with respect to the halogenated alkyl group for R⁴″.

Examples of hetero atoms include an oxygen atom, a nitrogen atom, and a sulfur atom.

Examples of the alkyl group as the substituent for R⁴″ include the same alkyl groups as those described above for the aforementioned “alkyl group which may have a substituent”.

In the group represented by formula X-Q¹-, Q¹ represents a divalent linking group containing an oxygen atom.

Q¹ may contain an atom other than an oxygen atom. Examples of atoms other than an oxygen atom include a carbon atom, a hydrogen atom, a sulfur atom and a nitrogen atom.

Examples of divalent linking groups containing an oxygen atom include non-hydrocarbon, oxygen atom-containing linking groups such as an oxygen atom (an ether bond; —O—), an ester bond (—C(═O)—O—), an amido bond (—C(═O)—NH—), a carbonyl group (—C(═O)—) and a carbonate group (—O—C(═O)—O—); and combinations of the aforementioned non-hydrocarbon, hetero atom-containing linking groups with an alkylene group.

Specific examples of the combinations of the aforementioned non-hydrocarbon, hetero atom-containing linking groups and an alkylene group include —R⁹¹—O—, —R⁹²—O—C(═O)—, —C(═O)—O—R⁹³— and —C(═O)—O—R⁹³—O—C(═O)— (in the formulas, each of R⁹¹ to R⁹³ independently represents an alkylene group).

The alkylene group for R⁹¹ to R⁹³ is preferably a linear or branched alkylene group, and preferably has 1 to 12 carbon atoms, more preferably 1 to 5, and most preferably 1 to 3.

Specific examples of alkylene groups include a methylene group [—CH₂—]; alkylmethylene groups such as —CH(CH₃)—, —CH(CH₂CH₃)—, —C(CH₃)₂—, —C(CH₃)(CH₂CH₃)—, —C(CH₃)(CH₂CH₂CH₃)— and —C(CH₂CH₃)₂—; an ethylene group [—CH₂CH₂—]; alkylethylene groups such as —CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂— and —CH(CH₂CH₃)CH₂—, and —C(CH₂CH₃)₂—CH₂—; a trimethylene group (n-propylene group) [—CH₂CH₂CH₂—]; alkyltrimethylene groups such as —CH(CH₃)CH₂CH₂— and —CH₂CH(CH₃)CH₂—; a tetramethylene group [—CH₂CH₂CH₂CH₂—]; alkyltetramethylene groups such as —CH(CH₃)CH₂CH₂CH₂— and —CH₂CH(CH₃)CH₂CH₂—; and a pentamethylene group [—CH₂CH₂CH₂CH₂CH₂—].

Q¹ is preferably a divalent linking group containing an ester linkage or ether linkage, and more preferably a group of —R⁹¹—O—, —R⁹²—O—C(═O)—, —C(═O)—O—, —C(═O)—O—R⁹³—, or —C(═O)—O—R⁹³—O—C(═O)—.

In the group represented by the formula X-Q¹-, the hydrocarbon group for X may be either an aromatic hydrocarbon group or an aliphatic hydrocarbon group.

The aromatic hydrocarbon group is a hydrocarbon group having an aromatic ring. The aromatic hydrocarbon ring preferably has 3 to 30 carbon atoms, more preferably 5 to 30, still more preferably 5 to 20, still more preferably 6 to 15, and most preferably 6 to 12. Here, the number of carbon atoms within a substituent(s) is not included in the number of carbon atoms of the aromatic hydrocarbon group.

Specific examples of aromatic hydrocarbon groups include an aryl group which is an aromatic hydrocarbon ring having one hydrogen atom removed therefrom, such as a phenyl group, a biphenyl group, a fluorenyl group, a naphthyl group, an anthryl group or a phenanthryl group; and an alkylaryl group such as a benzyl group, a phenethyl group, a 1-naphthylmethyl group, a 2-naphthylmethyl group, a 1-naphthylethyl group, or a 2-naphthylethyl group. The alkyl chain within the arylalkyl group preferably has 1 to 4 carbon atom, more preferably 1 or 2, and most preferably 1.

The aromatic hydrocarbon group may have a substituent. For example, part of the carbon atoms constituting the aromatic ring within the aromatic hydrocarbon group may be substituted with a hetero atom, or a hydrogen atom bonded to the aromatic ring within the aromatic hydrocarbon group may be substituted with a substituent.

In the former example, a heteroaryl group in which part of the carbon atoms constituting the ring within the aforementioned aryl group has been substituted with a hetero atom such as an oxygen atom, a sulfur atom or a nitrogen atom, and a heteroarylalkyl group in which part of the carbon atoms constituting the aromatic hydrocarbon ring within the aforementioned arylalkyl group has been substituted with the aforementioned heteroatom can be used.

In the latter example, as the substituent for the aromatic hydrocarbon group, an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, an oxygen atom (═O) or the like can be used.

The alkyl group as the substituent for the aromatic hydrocarbon group is preferably an alkyl group of 1 to 5 carbon atoms, and a methyl group, an ethyl group, a propyl group, an n-butyl group or a tert-butyl group is particularly desirable.

The alkoxy group as the substituent for the aromatic hydrocarbon group is preferably an alkoxy group having 1 to 5 carbon atoms, more preferably a methoxy group, ethoxy group, n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group, and most preferably a methoxy group or an ethoxy group.

Examples of the halogen atom as the substituent for the aromatic hydrocarbon group include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, and a fluorine atom is preferable.

Example of the halogenated alkyl group as the substituent for the aromatic hydrocarbon group includes a group in which part or all of the hydrogen atoms within the aforementioned alkyl group have been substituted with the aforementioned halogen atoms.

The aliphatic hydrocarbon group for X may be either a saturated aliphatic hydrocarbon group, or an unsaturated aliphatic hydrocarbon group. Further, the aliphatic hydrocarbon group may be linear, branched or cyclic.

In the aliphatic hydrocarbon group for X, a part of the carbon atoms constituting the aliphatic hydrocarbon group may be substituted with a substituent group containing a hetero atom, or a part or all of the hydrogen atoms constituting the aliphatic hydrocarbon group may be substituted with a substituent group containing a hetero atom.

As the “hetero atom” for X, there is no particular limitation as long as it is an atom other than a carbon atom and a hydrogen atom. Examples of hetero atoms include a halogen atom, an oxygen atom, a sulfur atom and a nitrogen atom. Examples of halogen atoms include a fluorine atom, a chlorine atom, an iodine atom and a bromine atom.

The substituent group containing a hetero atom may consist of a hetero atom, or may be a group containing a group or atom other than a hetero atom.

Specific examples of the substituent group for substituting part of the carbon atoms include —O—, —C(═O)—O—, —C(═O)—, —O—C(═O)—O—, —C(═O)—NH—, —NH— (the H may be replaced with a substituent such as an alkyl group or an acyl group), —S—, —S(═O)₂— and —S(═O)₂—O—. When the aliphatic hydrocarbon group is cyclic, the aliphatic hydrocarbon group may contain any of these substituent groups in the ring structure.

Examples of the substituent group for substituting part or all of the hydrogen atoms include an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group, an oxygen atom (═O) and a cyano group.

The aforementioned alkoxy group is preferably an alkoxy group having 1 to 5 carbon atoms, more preferably a methoxy group, ethoxy group, n-propoxy group, iso-propoxy group, n-butoxy group or tert-butoxy group, and most preferably a methoxy group or an ethoxy group.

Examples of the aforementioned halogen atom include a fluorine atom, a chlorine atom, a bromine atom and an iodine atom, and a fluorine atom is preferable.

Example of the aforementioned halogenated alkyl group includes a group in which part or all of the hydrogen atoms within an alkyl group of 1 to 5 carbon atoms (e.g., a methyl group, an ethyl group, a propyl group, an n-butyl group or a tert-butyl group) have been substituted with the aforementioned halogen atoms.

As the aliphatic hydrocarbon group, a linear or branched saturated hydrocarbon group, a linear or branched monovalent unsaturated hydrocarbon group, or a cyclic aliphatic hydrocarbon group (aliphatic cyclic group) is preferable.

The linear saturated hydrocarbon group (alkyl group) preferably has 1 to 20 carbon atoms, more preferably 1 to 15, and most preferably 1 to 10. Specific examples include a methyl group, an ethyl group, a propyl group, a butyl group, a pentyl group, a hexyl group, a heptyl group, an octyl group, a nonyl group, a decanyl group, an undecyl group, a dodecyl group, a tridecyl group, an isotridecyl group, a tetradecyl group, a pentadecyl group, a hexadecyl group, an isohexadecyl group, a heptadecyl group, an octadecyl group, a nonadecyl group, an icosyl group, a henicosyl group and a docosyl group.

The branched saturated hydrocarbon group (alkyl group) preferably has 3 to 20 carbon atoms, more preferably 3 to 15, and most preferably 3 to 10. Specific examples include a 1-methylethyl group, a 1-methylpropyl group, a 2-methylpropyl group, a 1-methylbutyl group, a 2-methylbutyl group, a 3-methylbutyl group, a 1-ethylbutyl group, a 2-ethylbutyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group and a 4-methylpentyl group.

The unsaturated hydrocarbon group preferably has 2 to 10 carbon atoms, more preferably 2 to 5, still more preferably 2 to 4, and most preferably 3. Examples of linear monovalent unsaturated hydrocarbon groups include a vinyl group, a propenyl group (an allyl group) and a butynyl group. Examples of branched monovalent unsaturated hydrocarbon groups include a 1-methylpropenyl group and a 2-methylpropenyl group.

Among the above-mentioned examples, as the unsaturated hydrocarbon group, a propenyl group is particularly desirable.

The aliphatic cyclic group may be either a monocyclic group or a polycyclic group. The aliphatic cyclic group preferably has 3 to 30 carbon atoms, more preferably 5 to 30, still more preferably 5 to 20, still more preferably 6 to 15, and most preferably 6 to 12.

As the aliphatic cyclic group, a group in which one or more hydrogen atoms have been removed from a monocycloalkane or a polycycloalkane such as a bicycloalkane, tricycloalkane or tetracycloalkane can be used. Specific examples include groups in which one or more hydrogen atoms have been removed from a monocycloalkane such as cyclopentane or cyclohexane; and groups in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane or tetracyclododecane.

When the aliphatic cyclic group does not contain a hetero atom-containing substituent group in the ring structure thereof, the aliphatic cyclic group is preferably a polycyclic group, more preferably a group in which one or more hydrogen atoms have been removed from a polycycloalkane, and a group in which one or more hydrogen atoms have been removed from adamantane is particularly desirable.

When the aliphatic cyclic group contains a hetero atom-containing substituent group in the ring structure thereof, the hetero atom-containing substituent group is preferably —O—, —C(═O)—O—, —S—, —S(═O)₂— or —S(═O)₂—O—. Specific examples of such aliphatic cyclic groups include groups represented by formulas (L1) to (L5) and (S1) to (S4) shown below.

In the formula, Q″ represents an alkylene group of 1 to 5 carbon atoms, —O—, —S—, —O—R⁹⁴— or —S—R⁹⁵— (wherein each of R⁹⁴ and R⁹⁵ independently represents an alkylene group of 1 to 5 carbon atoms); and m represents 0 or 1.

As the alkylene group for Q″, R⁹⁴ and R⁹⁵, the same alkylene groups as those described above for R⁹¹ to R⁹³ can be used.

In these aliphatic cyclic groups, part of the hydrogen atoms boned to the carbon atoms constituting the ring structure may be substituted with a substituent. Examples of substituents include an alkyl group, an alkoxy group, a halogen atom, a halogenated alkyl group, a hydroxyl group and an oxygen atom (═O).

As the alkyl group, an alkyl group of 1 to 5 carbon atoms is preferable, and a methyl group, an ethyl group, a propyl group, an n-butyl group or a tert-butyl group is particularly desirable.

As the alkoxy group and the halogen atom, the same groups as the substituent groups for substituting part or all of the hydrogen atoms can be used.

In the present invention, as X, a cyclic group which may have a substituent is preferable. The cyclic group may be either an aromatic hydrocarbon group which may have a substituent, or an aliphatic cyclic group which may have a substituent, and an aliphatic cyclic group which may have a substituent is preferable.

As the aromatic hydrocarbon group, a naphthyl group which may have a substituent, or a phenyl group which may have a substituent is preferable.

As the aliphatic cyclic group which may have a substituent, an aliphatic polycyclic group which may have a substituent is preferable. As the aliphatic polycyclic group, the aforementioned group in which one or more hydrogen atoms have been removed from a polycycloalkane, and groups represented by formulas (L2) to (L5), (S3) and (S4) are preferable.

In the present invention, R⁴″ preferably has X-Q¹- as a substituent. In such a case, R⁴″ is preferably a group represented by the formula X-Q¹-Y¹— (in the formula, Q¹ and X are the same as defined above; and Y¹ represents an alkylene group of 1 to 4 carbon atoms which may have a substituent, or a fluorinated alkylene group of 1 to 4 carbon atoms which may have a substituent).

In the group represented by the formula X-Q¹-Y¹—, as the alkylene group for Y¹, the same alkylene group as those described above for Q¹ in which the number of carbon atoms is 1 to 4 can be used.

As the fluorinated alkylene group, the aforementioned alkylene group in which part or all of the hydrogen atoms has been substituted with fluorine atoms can be used,

Specific examples of Y¹ include —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂—, —CF(CF₃)CF₂—, —CF(CF₂CF₃)—, —C(CF₃)₂—, —CF₂CF₂CF₂CF₂—, —CF(CF₃)CF₂CF₂—, —CF₂CF(CF₃)CF₂—, —CF(CF₃)CF(CF₃)—, —C(CF₃)₂CF₂—, —CF(CF₂CF₃)CF₂—, —CF(CF₂CF₂CF₃)—, —C(CF₃)(CF₂CF₃)—; —CHF—, —CH₂CF₂—, —CH₂CH₂CF₂—, —CH₂CF₂CF₂—, —CH(CF₃)CH₂—, —CH(CF₂CF₃)—, —C(CH₃)(CF₃)—, —CH₂CH₂CH₂CF₂—, —CH₂CH₂CF₂CF₂—, —CH(CF₃)CH₂CH₂—, —CH₂CH(CF₃)CH₂—, —CH(CF₃)CH(CF₃)—, —C(CF₃)₂CH₂—; —CH₂—, —CH₂CH₂—, —CH₂CH₂CH₂—, —CH(CH₃)CH₂—, —CH(CH₂CH₃)—, —C(CH₃)₂—, —CH₂CH₂CH₂CH₂—, —CH(CH₃)CH₂CH₂—, —CH₂CH(CH₃)CH₂—, —CH(CH₃)CH(CH₃)—, —C(CH₃)₂CH₂—, —CH(CH₂CH₃)CH₂—, —CH(CH₂CH₂CH₃)—, and —C(CH₃)(CH₂CH₃)—.

Y¹ is preferably a fluorinated alkylene group, and particularly preferably a fluorinated alkylene group in which the carbon atom bonded to the adjacent sulfur atom is fluorinated. Examples of such fluorinated alkylene groups include —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂—, —CF(CF₃)CF₂—, —CF₂CF₂CF₂CF₂—, —CF(CF₃)CF₂CF₂—, —CF₂CF(CF₃)CF₂—, —CF(CF₃)CF(CF₃)—, —C(CF₃)₂CF₂—, —CF(CF₂CF₃)CF₂—; —CH₂CF₂—, —CH₂CH₂CF₂—, —CH₂CF₂CF₂—; —CH₂CH₂CH₂CF₂—, —CH₂CH₂CF₂CF₂—, and —CH₂CF₂CF₂CF₂—.

Of these, —CF₂—, —CF₂CF₂—, —CF₂CF₂CF₂— or CH₂CF₂CF₂— is preferable, —CF₂—, —CF₂CF₂— or —CF₂CF₂CF₂— is more preferable, and —CF₂— is particularly desirable.

The alkylene group or fluorinated alkylene group may have a substituent. The alkylene group or fluorinated alkylene group “has a substituent” means that part or all of the hydrogen atoms or fluorine atoms in the alkylene group or fluorinated alkylene group has been substituted with groups other than hydrogen atoms and fluorine atoms.

Examples of substituents which the alkylene group or fluorinated alkylene group may have include an alkyl group of 1 to 4 carbon atoms, an alkoxy group of 1 to 4 carbon atoms, and a hydroxyl group.

In formula (b-2), R⁵″ and R⁶″ each independently represent an aryl group or alkyl group. At least one of R⁵″ and R⁶″ represents an aryl group. It is preferable that both of R⁵″ and R⁶″ represent an aryl group.

As the aryl group for R⁵″ and R⁶″, the same as the aryl groups for R¹″ to R³″ can be used.

As the alkyl group for R⁵″ and R⁶″, the same as the alkyl groups for R¹″ to R³″ can be used.

It is particularly desirable that both of R⁵″ and R⁶″ represents a phenyl group.

As R⁴″ in formula (b-2), the same groups as those mentioned above for R⁴″ in formula (b-1) can be used.

Specific examples of suitable onium salt acid generators represented by formula (b-1) or (b-2) include diphenyliodonium trifluoromethanesulfonate or nonafluorobutanesulfonate; bis(4-tert-butylphenyl)iodonium trifluoromethanesulfonate or nonafluorobutanesulfonate; triphenylsulfonium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; tri(4-methylphenyl)sulfonium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; dimethyl(4-hydroxynaphthyl)sulfonium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; monophenyldimethylsulfonium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; diphenylmonomethylsulfonium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; (4-methylphenyl)diphenylsulfonium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; (4-methoxyphenyl)diphenylsulfonium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; tri(4-tert-butyl)phenylsulfonium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; diphenyl(1-(4-methoxy)naphthyl)sulfonium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; di(1-naphthyl)phenylsulfonium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; 1-phenyltetrahydrothiophenium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; 1-(4-methylphenyl)tetrahydrothiophenium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; 1-(3,5-dimethyl-4-hydroxyphenyptetrahydrothiophenium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; 1-(4-methoxynaphthalene-1-yl)tetrahydrothiophenium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; 1-(4-ethoxynaphthalene-1-yl)tetrahydrothiophenium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; 1-(4-n-butoxynaphthalene-1-yl)tetrahydrothiophenium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; 1-phenyltetrahydrothiopyranium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; 1-(4-hydroxyphenyl)tetrahydrothiopyranium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; 1-(3,5-dimethyl-4-hydroxyphenyptetrahydrothiopyranium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate; and 1-(4-methylphenyl)tetrahydrothiopyranium trifluoromethanesulfonate, heptafluoropropanesulfonate or nonafluorobutanesulfonate.

It is also possible to use onium salts in which the anion moiety of these onium salts are replaced by an alkylsulfonate which may have a substituent, such as methanesulfonate, n-propanesulfonate, n-butanesulfonate, n-octanesulfonate, 1-adamantanesulfonate, 2-norbornanesulfonate, or d-camphor-10-sulfonate.

Furthermore, onium salts in which the anion moiety of these onium salts are replaced by an anion moiety represented by any one of formulas (1) to (b8) shown below can be used.

In the formulas, p represents an integer of 1 to 3; each of q1 and q2 independently represents an integer of 1 to 5; q3 represents an integer of 1 to 12; each of r1 and r2 independently represents an integer of 0 to 3; g represents an integer of 1 to 20; t3 represents an integer of 1 to 3; and R⁷ represents a substituent.

In the formulas, p, R⁷ and Q″ are the same as defined above; each of n1 to n5 independently represents 0 or 1; each of v1 to v5 independently represents an integer of 0 to 3; and each of w1 to w5 independently represents an integer of 0 to 3.

As the substituent for R⁷, the same groups as those which the aforementioned aliphatic hydrocarbon group or aromatic hydrocarbon group for X may have as a substituent can be used.

If there are two or more of the R⁷ group, as indicated by the values r1, r2, and w1 to w5, then the two or more of the R⁷ groups may be the same or different from each other.

Each of r1, r2, and w1 to w5 is preferably an integer of 0 to 2, and more preferably 0 or 1.

t3 is preferably 1 or 2, and most preferably 1.

q3 is preferably 1 to 5, more preferably 1 to 3, and most preferably 1.

Further, onium salt-based acid generators in which the anion moiety in general formula (b-1) or (b-2) is replaced by an anion moiety represented by general formula (b-3) or (b-4) shown below (the cation moiety is the same as (b-1) or (b-2)) may be used.

In formulas (b-3) and (b-4) above, X″ represents an alkylene group of 2 to 6 carbon atoms in which at least one hydrogen atom has been substituted with a fluorine atom; and each of Y″ and Z″ independently represents an alkyl group of 1 to 10 carbon atoms in which at least one hydrogen atom has been substituted with a fluorine atom.

X″ represents a linear or branched alkylene group in which at least one hydrogen atom has been substituted with a fluorine atom, and the alkylene group has 2 to 6 carbon atoms, preferably 3 to 5 carbon atoms, and most preferably 3 carbon atoms.

Each of Y″ and Z″ independently represents a linear or branched alkyl group in which at least one hydrogen atom has been substituted with a fluorine atom, and the alkyl group has 1 to 10 carbon atoms, preferably 1 to 7 carbon atoms, and most preferably 1 to 3 carbon atoms.

The smaller the number of carbon atoms of the alkylene group for X″ or those of the alkyl group for Y″ and Z″ within the above-mentioned range of the number of carbon atoms, the more the solubility in a resist solvent is improved.

Further, in the alkylene group for X″ or the alkyl group for Y″ and Z″, it is preferable that the number of hydrogen atoms substituted with fluorine atoms is as large as possible because the acid strength increases and the transparency to high energy radiation of 200 nm or less or electron beam is improved. The fluorination ratio of the alkylene group or alkyl group is preferably from 70 to 100%, more preferably from 90 to 100%, and it is particularly desirable that the alkylene group or alkyl group be a perfluoroalkylene group or perfluoroalkyl group in which all hydrogen atoms are substituted with fluorine atoms.

Furthermore, as an onium salt-based acid generator, a sulfonium salt having a cation moiety represented by general formula (b-5) or (b-6) shown below may be used.

In formulas (b-5) and (b-6) above, each of R⁴¹ to R⁴⁶ independently represents an alkyl group, an acetyl group, an alkoxy group, a carboxy group, a hydroxyl group or a hydroxyalkyl group; each of n₁ to n₅ independently represents an integer of 0 to 3; and n₆ represents an integer of 0 to 2.

With respect to R⁴¹ to R⁴⁶, the alkyl group is preferably an alkyl group of 1 to 5 carbon atoms, more preferably a linear or branched alkyl group, and most preferably a methyl group, ethyl group, propyl group, isopropyl group, n-butyl group or tert butyl group.

The alkoxy group is preferably an alkoxy group of 1 to 5 carbon atoms, more preferably a linear or branched alkoxy group, and most preferably a methoxy group or ethoxy group.

The hydroxyalkyl group is preferably the aforementioned alkyl group in which one or more hydrogen atoms have been substituted with hydroxy groups, and examples thereof include a hydroxymethyl group, a hydroxyethyl group and a hydroxypropyl group.

If there are two or more of an individual R⁴¹ to R⁴⁶ group, as indicated by the corresponding value of n₁ to n₆, then the two or more of the individual R⁴¹ to R⁴⁶ group may be the same or different from each other.

n₁ is preferably 0 to 2, more preferably 0 or 1, and still more preferably 0.

It is preferable that n₂ and n₃ each independently represent 0 or 1, and more preferably 0.

n₄ is preferably 0 to 2, and more preferably 0 or 1.

n₅ is preferably 0 or 1, and more preferably 0.

n₆ is preferably 0 or 1, and more preferably 1.

The anion moiety of the sulfonium salt having a cation moiety represented by general formula (b-5) or (b-6) is not particularly limited, and the same anion moieties for onium salt-based acid generators which have been proposed may be used. Examples of such anion moieties include fluorinated alkylsulfonic acid ions such as anion moieties (R⁴″SO₃ ⁻) for onium salt-based acid generators represented by general formula (b-1) or (b-2) shown above; and anion moieties represented by general formula (b-3) or (b-4) shown above.

In the present description, an oximesulfonate-based acid generator is a compound having at least one group represented by general formula (B-1) shown below, and has a feature of generating acid by irradiation. Such oximesulfonate acid generators are widely used for a chemically amplified resist composition, and can be appropriately selected.

In the formula, each of R³¹ and R³² independently represents an organic group.

The organic group for R³¹ and R³² refers to a group containing a carbon atom, and may include atoms other than carbon atoms (e.g., a hydrogen atom, an oxygen atom, a nitrogen atom, a sulfur atom, a halogen atom (such as a fluorine atom and a chlorine atom) and the like).

As the organic group for R³¹, a linear, branched, or cyclic alkyl group or aryl group is preferable. The alkyl group or the aryl group may have a substituent. The substituent is not particularly limited, and examples thereof include a fluorine atom and a linear, branched, or cyclic alkyl group having 1 to 6 carbon atoms. The alkyl group or the aryl group “has a substituent” means that part or all of the hydrogen atoms of the alkyl group or the aryl group is substituted with a substituent.

The alkyl group preferably has 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, still more preferably 1 to 8 carbon atoms, still more preferably 1 to 6 carbon atoms, and most preferably 1 to 4 carbon atoms. As the alkyl group, a partially or completely halogenated alkyl group (hereinafter, sometimes referred to as a “halogenated alkyl group”) is particularly desirable. The “partially halogenated alkyl group” refers to an alkyl group in which part of the hydrogen atoms are substituted with halogen atoms and the “completely halogenated alkyl group” refers to an alkyl group in which all of the hydrogen atoms are substituted with halogen atoms. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms and iodine atoms, and fluorine atoms are particularly desirable. In other words, the halogenated alkyl group is preferably a fluorinated alkyl group.

The aryl group preferably has 4 to 20 carbon atoms, more preferably 4 to 10 carbon atoms, and most preferably 6 to 10 carbon atoms. As the aryl group, partially or completely halogenated aryl group is particularly desirable. The “partially halogenated aryl group” refers to an aryl group in which some of the hydrogen atoms are substituted with halogen atoms and the “completely halogenated aryl group” refers to an aryl group in which all of hydrogen atoms are substituted with halogen atoms.

As R³¹, an alkyl group of 1 to 4 carbon atoms which has no substituent or a fluorinated alkyl group of 1 to 4 carbon atoms is particularly desirable.

As the organic group for R³², a linear, branched, or cyclic alkyl group, aryl group, or cyano group is preferable. Examples of the alkyl group and the aryl group for R³² include the same alkyl groups and aryl groups as those described above for R³¹.

As R³², a cyano group, an alkyl group of 1 to 8 carbon atoms having no substituent or a fluorinated alkyl group of 1 to 8 carbon atoms is particularly desirable.

Preferred examples of the oxime sulfonate acid generator include compounds represented by general formula (B-2) or (B-3) shown below.

In the formula, R³³ represents a cyano group, an alkyl group having no substituent or a halogenated alkyl group; R³⁴ represents an aryl group; and R³⁵ represents an alkyl group having no substituent or a halogenated alkyl group.

In the formula, R³⁶ represents a cyano group, an alkyl group having no substituent or a halogenated alkyl group; R³⁷ represents a divalent or trivalent aromatic hydrocarbon group; R³⁸ represents an alkyl group having no substituent or a halogenated alkyl group; and p″ represents 2 or 3.

In general formula (B-2), the alkyl group having no substituent or the halogenated alkyl group for R³³ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 6 carbon atoms.

As R³³, a halogenated alkyl group is preferable, and a fluorinated alkyl group is more preferable.

The fluorinated alkyl group for R³³ preferably has 50% or more of the hydrogen atoms thereof fluorinated, more preferably 70% or more, and most preferably 90% or more.

Examples of the aryl group for R³⁴ include groups in which one hydrogen atom has been removed from an aromatic hydrocarbon ring, such as a phenyl group, a biphenyl group, a fluorenyl group, a naphthyl group, an anthryl group, and a phenanthryl group, and heteroaryl groups in which some of the carbon atoms constituting the ring(s) of these groups are substituted with hetero atoms such as an oxygen atom, a sulfur atom, and a nitrogen atom. Of these, a fluorenyl group is preferable.

The aryl group for R³⁴ may have a substituent such as an alkyl group of 1 to 10 carbon atoms, a halogenated alkyl group, or an alkoxy group. The alkyl group and halogenated alkyl group as the substituent preferably has 1 to 8 carbon atoms, and more preferably 1 to 4 carbon atoms. Further, the halogenated alkyl group is preferably a fluorinated alkyl group.

The alkyl group having no substituent or the halogenated alkyl group for R³⁵ preferably has 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, and most preferably 1 to 6 carbon atoms.

As R³⁵, a halogenated alkyl group is preferable, and a fluorinated alkyl group is more preferable.

In terms of enhancing the strength of the acid generated, the fluorinated alkyl group for R³⁵ preferably has 50% or more of the hydrogen atoms fluorinated, more preferably 70% or more, still more preferably 90% or more. A completely fluorinated alkyl group in which 100% of the hydrogen atoms are substituted with fluorine atoms is particularly desirable.

In general formula (B-3), as the alkyl group having no substituent and the halogenated alkyl group for R³⁶, the same alkyl group having no substituent and the halogenated alkyl group described above for R³³ can be used.

Examples of the divalent or trivalent aromatic hydrocarbon group for R³⁷ include groups in which one or two hydrogen atoms have been removed from the aryl group for R³⁴.

As the alkyl group having no substituent or the halogenated alkyl group for R³⁸, the same one as the alkyl group having no substituent or the halogenated alkyl group for R³⁵ can be used.

p″ is preferably 2.

Specific examples of suitable oxime sulfonate acid generators include

-   α-(p-toluenesulfonyloxyimino)-benzyl cyanide, -   α-(p-chlorobenzenesulfonyloxyimino)-benzyl cyanide, -   α-(4-nitrobenzenesulfonyloxyimino)-benzyl cyanide, -   α-(4-nitro-2-trifluoromethylbenzenesulfonyloxyimino)-benzyl cyanide, -   α-(benzenesulfonyloxyimino)-4-chlorobenzyl cyanide, -   α-(benzenesulfonyloxyimino)-2,4-dichlorobenzyl cyanide, -   α-(benzenesulfonyloxyimino)-2,6-dichlorobenzyl cyanide, -   α-(benzenesulfonyloxyimino)-4-methoxybenzyl cyanide, -   α-(2-chlorobenzenesulfonyloxyimino)-4-methoxybenzyl cyanide, -   α-(benzenesulfonyloxyimino)-thien-2-yl acetonitrile, -   α-(4-dodecylbenzenesulfonyloxyimino)benzyl cyanide, -   α-[(p-toluenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile, -   α-[(dodecylbenzenesulfonyloxyimino)-4-methoxyphenyl]acetonitrile, -   α-(tosyloxyimino)-4-thienyl cyanide,     α-(methylsulfonyloxyimino)-1-cyclopentenyl acetonitrile,     α-(methylsulfonyloxyimino)-1-cyclohexenyl acetonitrile, -   α-(methylsulfonyloxyimino)-1-cycloheptenyl acetonitrile, -   α-(methylsulfonyloxyimino)-1-cyclooctenyl acetonitrile, -   α-(trifluoromethylsulfonyloxyimino)-1-cyclopentenyl acetonitrile, -   α-(trifluoromethylsulfonyloxyimino)-cyclohexyl acetonitrile, -   α-(ethylsulfonyloxyimino)-ethyl acetonitrile,     α-(propylsulfonyloxyimino)-propyl acetonitrile,     α-(cyclohexylsulfonyloxyimino)-cyclopentyl acetonitrile, -   α-(cyclohexylsulfonyloxyimino)-cyclohexyl acetonitrile, -   α-(cyclohexylsulfonyloxyimino)-1-cyclopentenyl acetonitrile, -   α-(ethylsulfonyloxyimino)-1-cyclopentenyl acetonitrile, -   α-(isopropylsulfonyloxyimino)-1-cyclopentenyl acetonitrile, -   α-(n-butylsulfonyloxyimino)-1-cyclopentenyl acetonitrile, -   α-(ethylsulfonyloxyimino)-1-cyclohexenyl acetonitrile, -   α-(isopropylsulfonyloxyimino)-1-cyclohexenyl acetonitrile, -   α-(n-butylsulfonyloxyimino)-1-cyclohexenyl acetonitrile, -   α-(methylsulfonyloxyimino)-phenyl acetonitrile, -   α-(methylsulfonyloxyimino)-p-methoxyphenyl acetonitrile, -   α-(trifluoromethylsulfonyloxyimino)-phenyl acetonitrile, -   α-(trifluoromethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile, -   α-(ethylsulfonyloxyimino)-p-methoxyphenyl acetonitrile, -   α-(propylsulfonyloxyimino)-p-methylphenyl acetonitrile, and -   α-(methylsulfonyloxyimino)-p-bromophenyl acetonitrile.

Further, oxime sulfonate-based acid generators disclosed in Japanese Unexamined Patent Application, First Publication No. Hei 9-208554 (Chemical Formulas 18 and 19 shown in paragraphs [0012] to [0014]) and oxime sulfonate-based acid generators disclosed in WO 2004/074242A2 (Examples 1 to 40 described at pages 65 to 85) may be preferably used.

Furthermore, as preferable examples, the following can be used.

Of the aforementioned diazomethane acid generators, specific examples of suitable bisalkyl or bisaryl sulfonyl diazomethanes include bis(isopropylsulfonyl)diazomethane, bis(p-toluenesulfonyl)diazomethane, bis(1,1-dimethylethylsulfonyl)diazomethane, bis(cyclohexylsulfonyl)diazomethane, and bis(2,4-dimethylphenylsulfonyl)diazomethane.

Further, diazomethane acid generators disclosed in Japanese Unexamined Patent Application, First Publication No. Hei 11-035551, Japanese Unexamined Patent Application, First Publication No. Hei 11-035552 and Japanese Unexamined Patent Application, First Publication No. Hei 11-035573 may be preferably used.

Furthermore, as examples of poly(bis-sulfonyl)diazomethanes, those disclosed in Japanese Unexamined Patent Application, First Publication No. Hei 11-322707, including 1,3-bis(phenylsulfonyldiazomethylsulfonyl)propane, 1,4-bis(phenylsulfonyldiazomethylsulfonyl)butane, 1,6-bis(phenylsulfonyldiazomethylsulfonyl)hexane, 1,10-bis(phenylsulfonyldiazomethylsulfonyl)decane, 1,2-bis(cyclohexylsulfonyldiazomethylsulfonyl)ethane, 1,3-bis(cyclohexylsulfonyldiazomethylsulfonyl)propane, 1,6-bis(cyclohexylsulfonyldiazomethylsulfonyl)hexane, and 1,10-bis(cyclohexylsulfonyldiazomethylsulfonyl)decane, may be given.

As the component (B), one type of acid generator may be used, or two or more types of acid generators may be used in combination.

In the present invention, as the component (B), it is preferable to use an onium salt having a fluorinated alkylsulfonic acid ion as the anion moiety.

In the positive resist composition of the present invention, the amount of the component (B) relative to 100 parts by weight of the component (A) is preferably 0.5 to 50 parts by weight, and more preferably 1 to 40 parts by weight. By ensuring that the amount of the component (B) is within the above-mentioned range, formation of a resist pattern can be satisfactorily performed. Further, by virtue of the above-mentioned range, a uniform solution can be obtained and the storage stability becomes satisfactory.

<Optional Components>

The positive resist composition of the present invention may further contain a nitrogen-containing organic compound (D) (hereafter referred to as the component (D)) as an optional component.

As the component (D), there is no particular limitation as long as it functions as an acid diffusion control agent, i.e., a quencher which traps the acid generated from the component (B) upon exposure. A multitude of these components (D) have already been proposed, and any of these known compounds may be used As the component (D), an amine such as an aliphatic amine, an aromatic amine or the like is preferable, an aliphatic amine is more preferable, and a secondary aliphatic amine or a tertiary aliphatic amine is particularly desirable. The term “aliphatic cyclic group” refers to a monocyclic group or polycyclic group that has no aromaticity. An aliphatic amine is an amine having one or more aliphatic groups, and the aliphatic groups preferably have 1 to 20 carbon atoms.

Examples of these aliphatic amines include amines in which at least one hydrogen atom of ammonia (NH₃) has been substituted with an alkyl group or hydroxyalkyl group of no more than 20 carbon atoms (i.e., alkylamines or alkylalcoholamines), and cyclic amines.

Specific examples of alkylamines and alkylalcoholamines include monoalkylamines such as n-hexylamine, n-heptylamine, n-octylamine, n-nonylamine, and n-decylamine; dialkylamines such as diethylamine, di-n-propylamine, di-n-heptylamine, di-n-octylamine, and dicyclohexylamine; trialkylamines such as trimethylamine, triethylamine, tri-n-propylamine, tri-n-butylamine, tri-n-hexylamine, tri-n-pentylamine, tri-n-heptylamine, tri-n-octylamine, tri-n-nonylamine, tri-n-decanylamine, and tri-n-dodecylamine; and alkyl alcohol amines such as diethanolamine, triethanolamine, diisopropanolamine, triisopropanolamine, di-n-octanolamine, tri-n-octanolamine, stearyldiethanolamine and laurildiethanolamine. Among these, trialkylamines and/or alkylalcoholamines are preferable.

Examples of the cyclic amine include heterocyclic compounds containing a nitrogen atom as a hetero atom. The heterocyclic compound may be a monocyclic compound (aliphatic monocyclic amine), or a polycyclic compound (aliphatic polycyclic amine).

Specific examples of the aliphatic monocyclic amine include piperidine, and piperazine.

The aliphatic polycyclic amine preferably has 6 to 10 carbon atoms, and specific examples thereof include 1,5-diazabicyclo[4.3.0]-5-nonene, 1,8-diazabicyclo[5.4.0]-7-undecene, hexamethylenetetramine, and 1,4-diazabicyclo[2.2.2]octane.

Examples of other aliphatic amines include tris(2-methoxymethoxyethyl)amine, tris{2-(2-methoxyethoxy)ethyl}amine, tris{2-(2-methoxyethoxymethoxy)ethyl}amine, tris{2-(1-methoxyethoxy)ethyl}amine, tris{2-(1-ethoxyethoxy)ethyl}amine, tris{2-(1-ethoxypropoxy)ethyl}amine and tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine.

Examples of aromatic amines include aniline, 1,8-naphthalenediamine, pyridine, 4-dimethylaminopyridine, pyrrole, indole, pyrazole, imidazole and derivatives thereof, as well as diphenylamine, triphenylamine and tribenzylamine.

These compounds can be used either alone, or in combinations of two or more different compounds.

The component (D) is typically used in an amount within a range from 0.01 to 5.0 parts by weight, relative to 100 parts by weight of the component (A). By ensuring that the amount of the component (D) is within the above-mentioned range, the shape of the resist pattern and the post exposure stability of the latent image formed by the pattern-wise exposure of the resist layer are improved.

Furthermore, in the positive resist composition of the present invention, for preventing any deterioration in sensitivity, and improving the resist pattern shape and the post exposure stability of the latent image formed by the pattern-wise exposure of the resist layer, at least one compound (E) (hereafter referred to as the component (E)) selected from the group consisting of an organic carboxylic acid, or a phosphorus oxo acid or derivative thereof can be added.

Examples of suitable organic carboxylic acids include acetic acid, malonic acid, citric acid, malic acid, succinic acid, benzoic acid, and salicylic acid.

Examples of phosphorus oxo acids or derivatives thereof include phosphoric acid, phosphonic acid and phosphinic acid. Among these, phosphonic acid is particularly desirable.

Examples of oxo acid derivatives include esters in which a hydrogen atom within the above-mentioned oxo acids is substituted with a hydrocarbon group. Examples of the hydrocarbon group include an alkyl group of 1 to 5 carbon atoms and an aryl group of 6 to 15 carbon atoms.

Examples of phosphoric acid derivatives include phosphoric acid esters such as di-n-butyl phosphate and diphenyl phosphate.

Examples of phosphonic acid derivatives include phosphonic acid esters such as dimethyl phosphonate, di-n-butyl phosphonate, phenylphosphonic acid, diphenyl phosphonate and dibenzyl phosphonate.

Examples of phosphinic acid derivatives include phosphinic acid esters such as phenylphosphinic acid.

As the component (E), one type may be used alone, or two or more types may be used in combination.

The component (E) is typically used in an amount within a range from 0.01 to 5.0 parts by weight, relative to 100 parts by weight of the component (A).

[Component (F)]

The positive resist composition of the present invention may include a fluorine-containing polymeric compound (F) (hereafter, referred to as “component (F)”). By including the component (F), the hydrophilicity/hydrophobicity of the resist film surface can be adjusted without impairing the lithography properties.

For example, by blending the component (F), the hydrophobicity of the resist film surface can be enhanced during exposure, thereby rendering the composition suitable for immersion exposure.

Further, by blending a component (F) having a base dissociable group (described later), since the component (F) exhibits enhanced hydrophilicity by the action of an alkali developing solution, the hydrophilicity of the surface of the resist film formed is enhanced during development.

Furthermore, by blending a component (F) having an acid dissociable group (described later), since the component (F) exhibits enhanced hydrophilicity by the action of acid generated from the component (B), the hydrophilicity of the exposed surface of the resist film formed is enhanced when conducting exposure and PEB.

When the component (F) is blended, it is preferable that the component (A) has no fluorine atom.

In the present invention, the component (F) preferably includes a structural unit (f1) represented by general formula (f1-1) shown below.

In formula (f1-1), R represents a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; Q⁰ represents a single bond or a divalent linking group; R⁷⁰ represents an organic group having a fluorine atom; and the plurality of R may be the same or different from each other.

(Structural Unit (f1))

In general formula (f1-1), R is the same as defined for R in general formula (a0-1), and a hydrogen atom or a methyl group is preferable.

In formula (f1-1), Q⁰ represents a single bond or a divalent linking group.

As examples of the divalent linking group for Q⁰, the same groups as those described above for R² in formula (a0-1) can be given. Preferable examples include a divalent hydrocarbon group which may have a substituent and a divalent linking group containing a hetero atom.

As the divalent hydrocarbon group which may have a substituent, a linear, branched or cyclic divalent aliphatic hydrocarbon group or a divalent aromatic hydrocarbon group is preferable, and a methylene group, and ethylene group, —CH(CH₃)—, a group in which one hydrogen atom has been removed from a tetracyclododecyl group, or an aromatic hydrocarbon group in which one hydrogen atom has been removed from a phenyl group is particularly desirable.

Among the aforementioned examples, as Q⁰, a single bond or a divalent linking group containing a hetero atom is preferable, and a single bond or a combination of a divalent non-hydrocarbon group containing a hetero atom with a divalent aliphatic hydrocarbon group is particularly desirable.

In general formula (f1-1), R⁷⁰ represents an organic group which may have a fluorine atom. However, when R⁷⁰ has no fluorine atom, Q⁰ has a fluorine atom.

An “organic group having a fluorine atom” refers to an organic group in which part or all of the hydrogen atoms have been substituted with a fluorine atom.

As an example of an organic group represented by R⁷⁰ which may have a fluorine atom, a hydrocarbon group which may have a fluorine atom can be given.

The hydrocarbon group which may have a fluorine atom may be linear, branched or cyclic.

R⁷⁰ preferably has 1 to 20 carbon atoms, more preferably 1 to 15 carbon atoms, and most preferably 1 to 10 carbon atoms.

It is preferable that the organic group having a fluorine atom represented by R⁷⁰ has 25% or more of the hydrogen atoms within the organic group fluorinated, more preferably 50% or more, and most preferably 60% or more, as the hydrophobicity of the resist film during immersion exposure is enhanced.

Preferable examples of R⁷⁰ include a base dissociable group, an acid dissociable group, and a group other than base dissociable groups and acid dissociable groups.

A base dissociable group refers to a group that is decomposable (—O—R⁷⁰ is dissociated) by the action of an alkali developing solution. The expression “decomposable in an alkali developing solution” means that the group is decomposable by the action of an alkali developing solution (preferably decomposable by action of a 2.38% by weight aqueous solution of tetramethylammonium hydroxide (TMAH) at 23° C.), and exhibits increased alkali solubility in the alkali developing solution. The reason for this is that the ester bond [—C(═O)—O—R⁷⁰] is decomposed (hydrolyzed) by the action of a base (alkali developing solution), thereby forming a hydrophilic group [—C(═O)—OH] (—O—R⁷⁰ is dissociated).

Preferable examples of the base dissociable group include fluorinated hydrocarbon groups which may or may not have a substituent. Among fluorinated hydrocarbon groups, a fluorinated, saturated hydrocarbon group or a fluorinated, unsaturated hydrocarbon group is preferable, and a fluorinated, saturated hydrocarbon group is particularly desirable.

R⁷⁰ may be linear, branched or cyclic, and is preferably linear or branched.

R⁷⁰ preferably has 1 to 20 carbon atoms, more preferably 1 to 15, still more preferably 1 to 10, and most preferably 1 to 5.

It is preferable that the organic group having a fluorine atom represented by R⁷⁰ has 25% or more of the hydrogen atoms within the organic group fluorinated, more preferably 50% or more, and most preferably 60% or more, as the hydrophobicity of the resist film during immersion exposure is enhanced.

An acid dissociable group is a group that is dissociated by an acid to increase solubility in an alkali developing solution. The acid dissociable group will be described later in detail. When the acid dissociable group contains no fluorine atom, Q⁰ has a fluorine atom.

Examples of the group other than acid dissociable groups and base dissociable groups include linear, branched or cyclic alkyl groups of 3 to 15 carbon atoms (excluding groups containing a tertiary carbon atom). In such a case, Q⁰ has a fluorine atom.

Acid Dissociable Group

The acid dissociable group for R⁷⁰ is not particularly limited as long as it is an organic group that is dissociable by the action of an acid, and examples thereof include a cyclic or chain-like tertiary alkyl ester-type acid dissociable group; and an acetal-type acid dissociable group, such as an alkoxyalkyl group. Among these, R⁷⁰ is preferably a tertiary alkyl ester-type acid dissociable group, and more preferably a structural unit represented by general formula (IV-1) shown below.

In formula (IV-1), at least one of R²⁰¹ represents a linear or branched alkyl group of 1 to 4 carbon atoms, and the or each remaining R²⁰¹ independently represents a linear or branched alkyl group of 1 to 4 carbon atoms or a monovalent aliphatic cyclic group of 4 to 20 carbon atoms, or the or each remaining R²⁰¹ may be mutually bonded to form a divalent aliphatic cyclic group of 4 to 20 carbon atoms together with the carbon atoms bonding each other; and the plurality of R²⁰¹ may be the same or different from each other.

As the aliphatic cyclic group for R²⁰¹ in general formula (IV-1), for example, a group in which one or more hydrogen atoms have been removed from a monocycloalkane or a polycycloalkane such as a bicycloalkane, a tricycloalkane or a tetracycloalkane can be used. Examples of such groups include groups in which one or more hydrogen atoms have been removed from a monocycloalkane such as cyclopentane or cyclohexane; and groups in which one or more hydrogen atoms have been removed from a polycycloalkane such as adamantane, norbornane, isobornane, tricyclodecane or tetracyclododecane. Specific examples of such groups include a cyclopentyl group, a cyclohexyl group, a norbornyl group and an adamantyl group.

Examples of linear or branched alkyl groups of 1 to 4 carbon atoms include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group and a tert-butyl group.

Examples of the acid dissociable group represented by general formula (IV-1) in which a plurality of R²⁰¹ each independently represents a linear or branched alkyl group of 1 to 4 carbon atoms include a tert-butyl group, a tert-pentyl group and a tert-hexyl group.

Examples of the acid dissociable group represented by general formula (IV-1) in which at least one of R²⁰¹ represents a linear or branched alkyl group of 1 to 4 carbon atoms, and the or each remaining R²⁰¹ independently represents a linear or branched alkyl group of 1 to 4 carbon atoms or a monovalent aliphatic cyclic group of 4 to 20 carbon atoms include a 1-(1-adamantyl)-1-methylethyl group, a 1-(1-adamantyl)-1-methylpropyl group, a 1-(1-adamantyl)-1-methylbutyl group, a 1-(1-adamantyl)-1-methylpentyl group, a 1-(1-cyclopentyl)-1-methylethyl group, a 1-(1-cyclopentyl)-1-methylpropyl group, a 1-(1-cyclopentyl)-1-methylbutyl group, a 1-(1-cyclopentyl)-1-methylpentyl group, a 1-(1-cyclohexyl)-1-methylethyl group, a 1-(1-cyclohexyl)-1-methylpropyl group, a 1-(1-cyclohexyl)-1-methylbutyl group, and a 1-(1-cyclohexyl)-1-methylpentyl group.

Examples of the acid dissociable group represented by general formula (IV-1) in which one R²⁰¹ group among the plurality of R²⁰¹ groups represents a linear or branched alkyl group of 1 to 4 carbon atoms, and the remaining two R²⁰¹ groups are mutually bonded to form a divalent aliphatic cyclic group of 4 to 20 carbon atoms together with the carbon atoms bonding each other include a 2-alkyl-2-adamantyl group such as a 2-methyl-2-adamantyl group or a 2-ethyl-2-adamantyl group, and a 1-alkyl-1-cycloalkyl group such as a 1-methyl-1-cyclopentyl group, a 1-ethyl-1-cyclopentyl group, a 1-methyl-1-cyclohexyl group, or a 1-ethyl-1-cyclohexyl group.

Among these examples, as the acid dissociable group represented by general formula (IV-1), a group in which one R²⁰¹ group among the plurality of R²⁰¹ groups represents a linear or branched alkyl group of 1 to 4 carbon atoms, and two of the R²⁰¹ groups are mutually bonded to form a divalent aliphatic cyclic group of 4 to 20 carbon atoms together with the carbon atoms bonding each other is preferable, and a 2-methyl-2-adamantyl group is particularly desirable.

Each R²⁰¹ group may have a substituent as long as the group represented by general formula (IV-1) functions as an acid dissociable group. As an example of the substituent, a halogen atom such as a fluorine atom can be given.

Specific examples of preferable units for the structural unit (f1) are shown below.

Hereinbelow, a structural unit in which R⁷⁰ in general formula (f1-1) represents a “base dissociable group” is referred to as a structural unit (f11), and a structural unit in which R⁷⁰ represents an acid dissociable group is referred to as a structural unit (f12).

(Structural Unit (f11))

Specific examples of preferable structural units for the structural unit (f11) include structural units represented by general formula (f11-1) or (f11-2) shown below.

In the formulas above, each R independently represents a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; Z represents a divalent organic group; A_(aryl) represents an aromatic cyclic group which may have a substituent; X₀₁ represents a single bond or a divalent linking group; and each R⁷¹ independently represents a base dissociable group. However, when R⁷¹ has no fluorine atom, Z has a fluorine atom in formula (f11-1), and A_(aryl) or X₀₁ has a fluorine atom in formula (f11-2).

In general formula (f11-1) or (f11-2), R is the same as defined above, and is preferably a hydrogen atom or a methyl group.

The base dissociable group for R⁷¹ is the same as defined in the explanation above, more preferably an alkyl group of 1 or 2 carbon atoms or a fluorinated hydrocarbon group of 1 to 5 carbon atoms, and a methyl group, —CH₂—CF₃, —CH₂—CF₂—CF₃, —CH(CF₃)₂, or —CH₂—CH₂—CF₂—CF₂—CF₂—CF₃ is particularly desirable. When R⁷¹ represents a methyl group, an ethyl group or a fluorinated hydrocarbon group, the —O—R⁷¹ group is a base dissociable group which is dissociable by the action of an alkali developing solution.

In general formula (f11-1), Z represents a divalent organic group.

Preferable examples of Z include the aforementioned hydrocarbon group which may have a substituent, and a group containing a hetero atom.

In general formula (f11-2), A_(aryl) represents an aromatic cyclic group which may have a substituent. A specific example of A_(aryl) includes an aromatic hydrocarbon ring (which may have a substituent) having two hydrogen atoms removed therefrom.

The ring skeleton of the aromatic cyclic group for A_(aryl) preferably has 6 to 15 carbon atoms. Examples of the ring skeleton include a benzene ring, a naphthalene ring, a phenanthrene ring and an anthracene ring. Among these, a benzene ring or a naphthalene ring is particularly desirable.

Examples of substituents which an aromatic cyclic group for A_(aryl) may have include a halogen atom, an alkyl group, an alkoxy group, a halogenated alkyl group of 1 to 5 carbon atoms, and an oxygen atom (═O). Examples of halogen atoms include a fluorine atom, a chlorine atom, an iodine atom and a bromine atom. As the substituent which an aromatic cyclic group for A_(aryl) may have, a fluorine atom is preferable.

A_(aryl) may be either an aromatic cyclic group having no substituent, or an aromatic cyclic group having a substituent, although an aromatic cyclic group having no substituent is preferable.

When A_(aryl) is an aromatic cyclic group having a substituent, the number of the substituent may be either 1 or at least 2, preferably 1 or 2, and more preferably 1.

In formula (f11-2), X₀₁ represents a single bond or a divalent linking group. Examples of divalent linking groups include an alkylene group of 1 to 10 carbon atoms, —O—, —C(═O)—, —C(═O)—O—, a carbonate bond (—O—C(═O)—O—), —NH—C(═O)—, and a combination of these groups, and a combination of —O— with an alkylene group of 1 to 10 carbon atoms is particularly desirable.

Examples of alkylene groups of 1 to 12 carbon atoms include linear, branched or cyclic alkylene groups, and a linear or branched alkylene group of 1 to 5 carbon atoms and a cyclic alkylene group of 4 to 12 carbon atoms are preferable.

X₀₁ is preferably a single bond, —(R⁷⁷)_(A0)—O—[C(═O)]_(b0)—R⁷⁸—, or —C(═O)—O—R⁷⁹—.

Each of R⁷⁷, R⁷⁸ and R⁷⁰ independently represents a linear, branched or cyclic alkylene group of 1 to 10 carbon atoms, and preferably a linear or branched alkylene group of 1 to 5 carbon atoms or a cyclic alkylene group of 4 to 10 carbon atoms.

a0 represents 0 or an integer of 1 to 5.

b0 represents 0 or 1.

Preferable examples of the structural unit (f11) include structural units represented by general formulas (f11-1-1) to (f11-1-5) or (f11-2-1) to (f11-2-4) shown below.

In general formulas (f11-1-1) to (f11-1-5) and (f11-2-1) to (f11-2-4), R and R⁷¹ are the same as defined above; each of R⁸¹ and R⁸² independently represents a hydrogen atom, a fluorine atom, an alkyl group of 1 to 5 carbon atoms or a fluorinated alkyl group of 1 to 5 carbon atoms; when a1 is 2 or more, the plurality of R⁸¹ and R⁸² may be the same or different from each other; each of a1 to a3, a5, a7, a9 and a11 to a13 independently represents an integer of 1 to 5 carbon atoms; each of a4, a6, a8 and a10 independently represents 0 or an integer of 1 to 5: b1 to b5 independently represents 0 or 1; R⁸⁰ represents a substituent; e represents an integer of 0 to 2; and A₁ represents a cyclic alkylene group of 4 to 20 carbon atoms.

In general formula (f11-1-1), a1 is preferably 1 to 3, more preferably 1 or 2.

In general formula (f11-1-2), it is preferable that each of a2 and a3 independently represent 1 to 3, more preferably 1 or 2. b1 represents 0 or 1.

In general formula (f11-1-3), a4 is preferably 0 or 1 to 3, more preferably 0, 1 or 2, and most preferably 0 or 1. a5 is preferably 1 to 3, more preferably 1 or 2. As the substituent for R⁸⁰, for example, a halogen atom, a lower alkyl group, an alkoxy group of 1 to 5 carbon atoms, a halogenated lower alkyl group, or an oxygen atom (═O) can be used. Examples of halogen atoms include a fluorine atom, a chlorine atom, an iodine atom and a bromine atom. e is preferably 0 or 1, and most preferably 0 from an industrial viewpoint. b2 is preferably 0.

In general formula (f11-1-4), a6 is preferably 0 or 1 to 3, more preferably 0, 1 or 2, and most preferably 0 or 1. a7 is preferably 1 to 3, more preferably 1 or 2. b3 is preferably 0. R⁸⁰ and e are the same as defined above.

In general formula (f11-1-5), A₁ represents a cyclic alkylene group of 4 to 20 carbon atoms, preferably a cyclic alkylene group of 5 to 15 carbon atoms, and more preferably a cyclic alkylene group of 6 to 12 carbon atoms. Specific examples include the aforementioned “cyclic aliphatic hydrocarbon groups” described above in relation to the aforementioned hydrocarbon group which may have a substituent.

In general formula (f11-2-1), a8 is preferably 0 or 1 to 3, more preferably 0, 1 or 2, and most preferably 0 or 1. a9 is preferably 1 to 3, more preferably 1 or 2. b4 is preferably 0. R⁸⁰ and e are the same as defined above.

In general formula (f11-2-2), a10 is preferably 0 or 1 to 3, more preferably 0, 1 or 2, and most preferably 0 or 1. a11 is preferably 1 to 3, more preferably 1 or 2. b5 is preferably 0. R⁸⁰ and e are the same as defined above.

In general formula (f11-2-3), a12 is preferably 1 to 3, more preferably 1 or 2. R⁸⁰ and e are the same as defined above.

In general formula (f11-2-4), a13 is preferably 1 to 3, more preferably 1 or 2. R⁸⁰ and e are the same as defined above.

Specific examples of structural units represented by the above general formulas (f11-1-1) to (f11-1-5) and (f11-2-1) to (f11-2-4) are shown below.

As the structural unit (f11), at least one structural unit selected from the group consisting of structural units represented by general formulas (f11-1-1) to (f11-1-5) and (f11-2-1) to (f11-2-4) is preferable, more preferably at least one structural unit selected from the group consisting of structural units represented by general formulas (f11-1-1) to (f-1-1-5), (f11-2-1) and (f11-2-2), and most preferably at least one structural unit selected from the group consisting of structural units represented by general formulas (f11-1-1), (f11-1-5) and (f11-2-2).

As the structural unit (f11), one type of structural unit may be used alone, or two or more structural units may be used in combination.

In the component (F), the amount of the structural unit (f11) based on the combined total of all structural units constituting the component (F) is preferably 10 to 90 mol %, more preferably 20 to 90 mol %, still more preferably 30 to 90 mol %, and may be even 100 mol %. When the amount of the structural unit (f11) is at least as large as the lower limit of the above-mentioned range, in the formation of a resist pattern, the hydrophobicity during immersion exposure is enhanced.

(Structural Unit (f12))

Specific examples of preferable structural units for the structural unit (f12) include structural units represented by general formula (f12-1) shown below.

In formula (f12-1), R represents a hydrogen atom, an alkyl group of 1 to 5 carbon atoms or a halogenated alkyl group of 1 to 5 carbon atoms; Q⁰′ represents a single bond or a divalent linking group; and R⁷² represents an acid dissociable group.

In general formula (f12-1), R is the same as defined above, and is preferably a hydrogen atom or a methyl group.

Examples of the acid dissociable group for R⁷² include the same groups as those described above in the explanation of the acid dissociable group for R⁷⁰.

Preferable examples of a structural unit represented by general formula (f12-1) in which Q⁰′ is a single bond include structural units represented by general formulas (f12-1-1) to (f12-1-4) shown below.

In general formula (f12-1), when Q⁰′ represents a divalent linking group, examples of the divalent linking group include the same groups as those described above for X₀₁ in general formula (f11-2), and a divalent aromatic hydrocarbon group. Examples of divalent aromatic hydrocarbon groups include aromatic hydrocarbon groups of 6 to 20 carbon atoms such as groups in which two hydrogen atoms have been removed from a benzene ring, a naphthalene ring or an anthracene ring.

In a structural unit (f12), Q⁰′ is preferably a single bond or —C(═O)—O—R^(d)— (in the formula, R^(d) represents a linear or branched alkylene group of 1 to 10 carbon atoms which may contain an oxygen atom, and the alkylene group may be fluorinated), and more preferably a single bond.

Preferable examples of a structural unit represented by general formula (f12-1) in which Q⁰′ is —C(═O)—O—R^(d)— include structural units represented by general formulas (f12-1-5) to (f12-1-11) shown below.

In the formulas shown below, R is the same as defined above, and is preferably a hydrogen atom or a methyl group.

As the structural unit (f12), at least one structural unit selected from the group consisting of structural units represented by general formulas (f12-1-1) to (f12-1-11) are preferable, and at least one structural unit selected from the group consisting of structural units represented by general formulas (f12-1-1) to (f12-1-4) is particularly desirable.

In the component (F), as the structural unit (f12), one type of structural unit may be used alone, or two or more types of structural units may be used in combination.

When the component (F) includes the structural unit (f12), the amount of the structural unit (f12) based on the combined total of all structural units constituting the component (F) is preferably 10 to 100 mol %, more preferably 30 to 90 mol %, and most preferably 50 to 90 mol %. When the amount of the structural unit (f12) is at least as large as the lower limit of the above-mentioned range, in the formation of a resist pattern, the hydrophobicity during exposure is enhanced. Further, the lithographic properties are also improved. On the other hand, by when the amount is no more than the upper limit of the above-mentioned range, a good balance can be achieved with the other structural units. The structural unit (f12) can be used as a homopolymer.

[Other Structural Unit]

The component (F) may contain a structural unit other than the aforementioned structural unit (f1) (hereafter, referred to as “structural unit (f2)”), as long as the effects of the present invention are not impaired.

Preferable examples of the structural unit (f2) include the same structural units as those described above for the structural unit (a1). A structural unit represented by the aforementioned formula (a1-0-11) is more preferable.

In formula (a1-0-11) for the structural unit (f2), the alkyl group represented by R²¹ is preferably an ethyl group, an n-propyl group or an n-butyl group.

The aliphatic monocyclic group formed by R²² and the carbon atom bonded thereto is preferably a 8- to 11-membered ring, and more preferably a 8- to 10-membered ring.

In the component (F), as the structural unit (f2), one type of structural unit may be used alone, or two or more types of structural units may be used in combination.

When the component (F) includes the structural unit (f2), the amount of the structural unit (f2) based on the combined total of all structural units constituting the component (F) is preferably 5 to 80 mol %, more preferably 10 to 60 mol %, still more preferably 15 to 50 mol %, and most preferably 20 to 40 mol %. When the amount of the structural unit (f2) is at least as large as the lower limit of the above-mentioned range, the characteristic feature of exhibiting hydrophobicity during immersion exposure, but then exhibiting increased hydrophilicity during exposure and post exposure baking (PEB) is improved. Moreover, formation of bridge-type defects in a line and space pattern or formation of “Not Open” defects in which a portion of, or all of, a contact hole pattern is not open can be suppressed. Furthermore, the proportion of hydrocarbon groups within the component (F) increases and the water tracking ability during immersion exposure using a scanning-type immersion exposure apparatus is improved. On the other hand, when the amount is no more than the upper limit of the above-mentioned range, a good balance can be achieved with the structural unit (f1).

The component (F) may include a structural unit other than the structural unit (f1) and the structural unit (f2) (hereafter, frequently referred to as “structural unit (f3)”), as long as the effects of the present invention are not impaired.

There are no particular limitations on the structural unit (f3), provided the structural unit is derived from a compound that is copolymerizable with the compound that derives the structural unit (f1) and the compound that derives the structural unit (f2). Examples of such structural units include structural units which have been proposed for the base resin of a conventional chemically amplified resist (such as the aforementioned structural units (a2) to (a4) which do not fall under the category of the structural units (f1) and (f2)).

In the component (F), as the structural unit (f3), one type of structural unit may be used alone, or two or more types of structural units may be used in combination.

When the component (F) includes the structural unit (f3), the amount of the structural unit (f3) based on the combined total of all structural units constituting the component (F) is preferably 1 to 25 mol %, more preferably 5 to 20 mol %, and most preferably 10 to 20 mol %.

In the present invention, the component (F) is preferably a polymer including the structural unit (f11), a polymer including the structural unit (f12), or a polymer including the structural unit (f1).

Examples of such polymers include a polymer consisting of one structural unit (f11), a copolymer consisting of at least two structural units (f11), a polymer consisting of one structural unit (f12), and a copolymer consisting of a structural unit (f11) and a structural unit (f2).

The weight average molecular weight (Mw) (the polystyrene equivalent value determined by gel permeation chromatography) of the component (F) is not particularly limited, but is preferably 2,000 to 50,000, more preferably 3,000 to 30,000, and most preferably 4,000 to 25,000. When the weight average molecular weight is no more than the upper limit of the above-mentioned range, the resist composition exhibits a satisfactory solubility in a resist solvent. On the other hand, when the weight average molecular weight is at least as large as the lower limit of the above-mentioned range, dry etching resistance and the cross-sectional shape of the resist pattern becomes satisfactory.

Further, the dispersity (Mw/Mn) is preferably 1.0 to 5.0, more preferably 1.0 to 3.0, and most preferably 1.2 to 2.5. Here, Mn is the number average molecular weight.

As the component (F), one type of resin may be used, or two or more types of resins may be used in combination.

In the positive resist composition of the present invention, the amount of the component (F) relative to 100 parts by weight of the component (A) is preferably 0.1 to 50 parts by weight, more preferably 0.1 to 40 parts by weight, still more preferably 0.5 to 30 parts by weight, and most preferably 0.5 to 15 parts by weight.

When the amount of the component (F) is at least as large as the lower limit of the above-mentioned range, the effects of blending the component (F) can be satisfactorily achieved. On the other hand, by ensuring that the amount of the component (F) is no more than the upper limit of the above-mentioned range, the lithography properties are improved.

If desired, other miscible additives can also be added to the positive resist composition of the present invention. Examples of such miscible additives include additive resins for improving the performance of the resist film, surfactants for improving the applicability, dissolution inhibitors, plasticizers, stabilizers, colorants, halation prevention agents, and dyes.

The positive resist composition of the present invention can be prepared by dissolving the materials for the resist composition in an organic solvent (hereafter, frequently referred to as “component (S)”).

The component (S) may be any organic solvent which can dissolve the respective components to give a uniform solution, and one or more kinds of any organic solvent can be appropriately selected from those which have been conventionally known as solvents for a chemically amplified resist.

Examples thereof include lactones such as γ-butyrolactone;

ketones such as acetone, methyl ethyl ketone, cyclohexanone, methyl-n-pentyl ketone, methyl isopentyl ketone, and 2-heptanone;

polyhydric alcohols, such as ethylene glycol, diethylene glycol, propylene glycol and dipropylene glycol;

compounds having an ester bond, such as ethylene glycol monoacetate, diethylene glycol monoacetate, propylene glycol monoacetate, and dipropylene glycol monoacetate; polyhydric alcohol derivatives including compounds having an ether bond, such as a monoalkylether (e.g., monomethylether, monoethylether, monopropylether or monobutylether) or monophenylether of any of these polyhydric alcohols or compounds having an ester bond (among these, propylene glycol monomethyl ether acetate (PGMEA) and propylene glycol monomethyl ether (PGME) are preferable);

cyclic ethers such as dioxane; esters such as methyl lactate, ethyl lactate (EL), methyl acetate, ethyl acetate, butyl acetate, methyl pyruvate, ethyl pyruvate, methyl methoxypropionate, and ethyl ethoxypropionate;

and aromatic organic solvents such as anisole, ethylbenzylether, cresylmethylether, diphenylether, dibenzylether, phenetole, butylphenylether, ethylbenzene, diethylbenzene, pentylbenzene, isopropylbenzene, toluene, xylene, cymene and mesitylene.

These solvents can be used individually, or in combination as a mixed solvent.

Among these, propylene glycol monomethyl ether acetate (PGMEA), propylene glycol monomethyl ether (PGME) and ethyl lactate (EL) are preferable.

Further, among the mixed solvents, a mixed solvent obtained by mixing PGMEA with a polar solvent is preferable. The mixing ratio (weight ratio) of the mixed solvent can be appropriately determined, taking into consideration the compatibility of the PGMEA with the polar solvent, but is preferably in the range of 1:9 to 9:1, more preferably from 2:8 to 8:2.

Specifically, when EL is mixed as the polar solvent, the PGMEA:EL weight ratio is preferably from 1:9 to 9:1, and more preferably from 2:8 to 8:2. Alternatively, when PGME is mixed as the polar solvent, the PGMEA:PGME is preferably from 1:9 to 9:1, more preferably from 2:8 to 8:2, and still more preferably 3:7 to 7:3.

Further, as the component (S), a mixed solvent of at least one of PGMEA and EL with γ-butyrolactone is also preferable. The mixing ratio (former:latter) of such a mixed solvent is preferably from 70:30 to 95:5.

The amount of the organic solvent is not particularly limited, and is appropriately adjusted to a concentration which enables coating of a coating solution to a substrate, depending on the thickness of the coating film. In general, the organic solvent is used in an amount such that the solid content of the resist composition becomes within the range from 1 to 20% by weight, and preferably from 2 to 15% by weight.

The positive resist composition of the present invention described above and the component (A1) or (A1′) blended in the positive resist composition are novel, and are essentially unknown in the art.

By the positive resist composition of the present invention, a resist film can be formed on a support such as a substrate with excellent adhesion.

Further, by the positive resist composition of the present invention, the formed pattern exhibits excellent properties with respect to the pattern shape (e.g., circularity of the holes of a hole pattern), in-plane uniformity (CDU), line width roughness (LWR), rectangularity of the cross-section, and the like. LWR refers to the phenomenon in which the line widths of a line pattern formed using a resist composition becomes heterogeneous, and improvement in this characteristic becomes more important as the pattern becomes finer.

Further, by the positive resist composition of the present invention, a resist pattern can be formed with excellent mask reproducibility (e.g., excellent mask error factor (MEF)). The MEF is a parameter that indicates how faithfully mask patterns of differing dimensions can be reproduced by using the same exposure dose with fixed pitch and changing the mask size (i.e., mask reproducibility).

Further, in the formation of a resist pattern using the positive resist composition of the present invention, the problems of scums generated as residue of the exposed portions of the resist film which cannot be satisfactorily dissolved in an alkali developing solution can be solved.

In the present invention, the reasons why the above-mentioned effects can be achieved have not been elucidated yet. However, one of the reasons is presumed that by virtue of the structural unit (a0) having a specific lactone-containing cyclic group bonded to the terminal of a relatively long side chain, the component (B) can be uniformly distributed in the resist film, thereby resulting in the improvement in lithography properties.

Further, in the positive resist composition of the present invention, the hydrophilicity of the resist film surface is increased upon coming into contact with an alkali developing solution. Therefore, when a resist film formed using the positive resist composition is subjected to exposure and alkali developing, the hydrophilicity of the unexposed portions is increased.

In conventional techniques, when the resist film exhibits high hydrophobicity, defects (water mark defects caused by the influence of the immersion medium such as water, bridge defects, not-open defects, adhesion-type defects) are likely to be generated on the resist film surface following developing. In contrast, in the resist film formed using the positive resist composition of the present invention, since the hydrophilicity of the resist film surface of unexposed portions is increased during alkali developing, generation of defects can be reduced. In the present invention, effect of reducing generation of adhesion-type defects is particularly expected.

<<Method of Forming a Resist Pattern>>

The method of forming a resist pattern according to the present invention includes: applying a positive resist composition of the present invention to a substrate to form a resist film on the substrate; conducting exposure of the resist film; and developing the resist film to form a resist pattern.

More specifically, the method for forming a resist pattern according to the present invention can be performed, for example, as follows.

More specifically, the method for forming a resist pattern according to the present invention can be performed, for example, as follows. Firstly, a positive resist composition of the present invention is applied onto a substrate using a spinner or the like, and a prebake (post applied bake (PAB)) is conducted under temperature conditions of 80 to 150° C. for 40 to 120 seconds, preferably 60 to 90 seconds to form a resist film. Then, for example, using an ArF exposure apparatus or the like, the resist film is selectively exposed with an ArF exposure apparatus, an electron beam exposure apparatus, an EUV exposure apparatus or the like through a mask pattern or directly irradiated with electron beam without a mask pattern, followed by post exposure bake (PEB) under temperature conditions of 80 to 150° C. for 40 to 120 seconds, preferably 60 to 90 seconds. Subsequently, developing is conducted using an alkali developing solution such as a 0.1 to 10% by weight aqueous solution of tetramethylammonium hydroxide (TMAH), preferably followed by rinsing with pure water, and drying. If desired, bake treatment (post bake) can be conducted following the developing. In this manner, a resist pattern that is faithful to the mask pattern can be obtained.

The substrate is not specifically limited and a conventionally known substrate can be used. For example, substrates for electronic components, and such substrates having wiring patterns formed thereon can be used. Specific examples of the material of the substrate include metals such as silicon wafer, copper, chromium, iron and aluminum; and glass Suitable materials for the wiring pattern include copper, aluminum, nickel, and gold.

Further, as the substrate, any one of the above-mentioned substrates provided with an inorganic and/or organic film on the surface thereof may be used. As the inorganic film, an inorganic antireflection film (inorganic BARC) can be used. As the organic film, an organic antireflection film (organic BARC) can be used.

The wavelength to be used for exposure is not particularly limited and the exposure can be conducted using radiation such as ArF excimer laser, KrF excimer laser,

F₂ excimer laser, extreme ultraviolet rays (EUV), vacuum ultraviolet rays (VUV), electron beam (EB), X-rays, and soft X-rays. The positive resist composition of the present invention is effective to KrF excimer laser, ArF excimer laser, EB and EUV, and particularly effective to ArF excimer laser.

The exposure of the resist film can be either a general exposure (dry exposure) conducted in air or an inert gas such as nitrogen, or immersion exposure (immersion lithography).

In immersion lithography, the region between the resist film and the lens at the lowermost point of the exposure apparatus is pre-filled with a solvent (immersion medium) that has a larger refractive index than the refractive index of air, and the exposure (immersion exposure) is conducted in this state.

The immersion medium preferably exhibits a refractive index larger than the refractive index of air but smaller than the refractive index of the resist film to be exposed. The refractive index of the immersion medium is not particularly limited as long at it satisfies the above-mentioned requirements.

Examples of this immersion medium which exhibits a refractive index that is larger than the refractive index of air but smaller than the refractive index of the resist film include water, fluorine-based inert liquids, silicon-based solvents and hydrocarbon-based solvents.

Specific examples of the fluorine-based inert liquids include liquids containing a fluorine-based compound such as C₃HCl₂F₅, C₄F₉OCH₃, C₄F₉OC₂H₅ or C₅H₃F₇ as the main component, which have a boiling point within a range from 70 to 180° C. and preferably from 80 to 160° C. A fluorine-based inert liquid having a boiling point within the above-mentioned range is advantageous in that the removal of the immersion medium after the exposure can be conducted by a simple method.

As a fluorine-based inert liquid, a perfluoroalkyl compound in which all of the hydrogen atoms of the alkyl group are substituted with fluorine atoms is particularly desirable. Examples of these perfluoroalkyl compounds include perfluoroalkylether compounds and perfluoroalkylamine compounds.

Specifically, one example of a suitable perfluoroalkylether compound is perfluoro(2-butyl-tetrahydrofuran) (boiling point 102° C.), and an example of a suitable perfluoroalkylamine compound is perfluorotributylamine (boiling point 174° C.).

As the immersion medium, water is preferable in terms of cost, safety, environment and versatility.

<<Polymeric Compound>>

The polymeric compound of the present invention includes a component (A1′) containing an acid dissociable, dissolution inhibiting group within the structure thereof and including a structural unit (a0) represented by general formula (a0-1) shown below and a structural unit (a2) derived from an acrylate ester containing a lactone-containing cyclic group exclusive of the structural unit (a0); or a component (A1) including a structural unit (a0) represented by general formula (a0-1) shown below and a structural unit (a1) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group exclusive of the structural unit (a0) and the structural unit (a2).

The explanation of the polymeric compound of the present invention is the same as the explanation of the components (A1) and (A1′) of the positive resist composition of the present invention described above.

In the formula, R¹ represents a hydrogen atom, a lower alkyl group or a halogenated lower alkyl group; R² represents a divalent linking group; each R′ independently represents a hydrogen atom, an alkyl group of 1 to 5 carbon atoms, an alkoxy group of 1 to 5 carbon atoms or —COOR″, wherein R″ represents a hydrogen atom or an alkyl group; and A″ represents an oxygen atom, a sulfur atom, or an alkylene group of 1 to 5 carbon atoms which may contain an oxygen atom or a sulfur atom.

Examples

As follows is a description of examples of the present invention, although the scope of the present invention is by no way limited by these examples.

In the following examples, a unit represented by a chemical formula (1) is designated as “compound (1)”, and the same applies for compounds represented by other formulas.

Monomer Synthesis Example 1 Synthesis of Compound (2)

The compound (2) used in the polymer synthesis examples described later was synthesized as follows.

300 ml of a THF solution containing 30.23 g (151.71 mmol) of an alcohol (1), 30.23 g (157.71 mmol) of ethyldiisopropylaminocarbodiimide (EDCI) hydrochloride and 0.6 g (5 mmol) of dimethylaminopyridine was added to a 500 ml three-necked flask in nitrogen atmosphere, and 16.67 g (115.66 mmol) of a precursor (1) was added thereto while cooling with ice (0° C.), followed by stirring at room temperature for 12 hours.

After conducting thin-layer chromatography to confirm that the raw materials had been consumed, 50 ml of water was added to stop the reaction. Then, the reaction solvent was concentrated under reduced pressure, and extraction was conducted with ethyl acetate. The obtained organic phase was washed with saturated sodium hydrogencarbonate and water. Thereafter, the solvent was distilled off under reduced pressure, and the resulting product was dried, thereby obtaining 26.06 g of the compound (2). The results of instrumental analysis of the obtained compound (2) were as follows.

¹H-NMR(CDCl₃,400 MHz): δ(ppm)=6.23 (s,1H,Ha or b), 5.67 (s,1H,Ha or b), 4.40-4.71 (m,3H,Hd,He), 1.38-2.74 (m,15H,Hc,Hf,Hg,Hh,Hi,Hj,Hk,Hl)

Monomer Synthesis Example 1-2 Synthesis of Compound (2′)

The same procedure as in Monomer Synthesis Example 1 was performed, except that the alcohol (1) was changed to alcohol (1′) shown below, thereby obtaining a compound (2′).

The results of instrumental analysis of the obtained compound (2′) were as follows.

¹H-NMR(CDCl₃,400 MHz): δ(ppm)=6.13 (s,1H,Ha or Hb), 5.58 (t,1H,Ha or Hb), 4.96 (s,1H,He or Hf), 4.60 (s,2H,Hd), 4.06 (d,1H,He or Hf), 3.72 (m,2H,Hl), 3.63 (s,3H,Hm), 2.47-2.87 (m,4H,Hg,Hi,Hj,Hk), 1.90 (s,3H,Hc), 1.79 (d,1H,Hh), 1.49 (d,1H,Hh)

Monomer Synthesis Example 2 Synthesis of Compound (11)

The compound (11) used in the polymer synthesis examples described later was synthesized as follows.

37.6 g (494 mmol) of glycolic acid, 700 mL of DMF, 86.5 g (626 mmol) of potassium carbonate, and 28.3 g (170 mmol) of potassium iodide were added to a 2 L three-necked flask equipped with a thermometer, a cooling pipe, and a stirrer, followed by stirring at room temperature for 30 minutes. Then, 300 ml of a dimethylformamide solution containing 100 g (412 mmol) of 2-methyl-2-adamantyl chloroacetate was gradually added thereto. The resultant was heated to 40° C., and stirred for 4 hours. Subsequently, 2,000 ml of diethylether was added to the reaction mixture, followed by filtration. The resulting solution was washed with 500 ml of distilled water three times. Then, crystallization was conducted using a mixed solvent containing 300 ml of toluene and 200 ml of heptane, thereby obtaining 78 g of an objective compound (2-(2-(2-methyl-2-adamantyloxy)-2-oxoethoxy)-2-oxoethanol) in the form of a colorless solid (yield: 67%, GC purity: 99%).

The results of instrumental analysis of the obtained compound were as follows.

¹H-NMR: 1.59 (d,2H,J=12.5 Hz), 1.64 (s,3H),1.71-1.99 (m,10H), 2.29 (m,2H), 2.63 (t,1H,J=5.2 Hz), 4.29 (d,2H,J=5.2 Hz), 4.67 (s,2H)

¹³C-NMR: 22.35, 26.56, 27.26, 32.97, 34.54, 36.29, 38.05, 60.54, 61.50, 89.87, 165.97, 172.81

GC-MS: 282 (M+,0.02%), 165 (0.09%), 149 (40%), 148 (100%), 133 (22%), 117 (2.57%), 89 (0.40%)

From the results above, it was confirmed that the obtained compound was 2-(2-(2-methyl-2-adamantyloxy)-2-oxoethoxy)-2-oxoethanol.

Subsequently, 165 g (584 mmol) of 2-(2-(2-methyl-2-adamantyloxy)-2-oxoethoxy)-2-oxoethanol, 2,000 ml of THF, 105 ml (754 mmol) of triethylamine, and 0.165 g (1,000 ppm) of p-methoxyphenol were added to and dissolved in a 2 L three-necked flask equipped with a thermometer, a cooling pipe, and a stirrer.

Then, 62.7 ml (648 mmol) of methacryloyl chloride was gradually added thereto while cooling in an ice bath. The temperature of the resultant was elevated to room temperature, and the resultant was stirred for 3 hours. Subsequently, 1,000 ml of diethylether was added thereto, followed by washing with 200 ml of distilled water 5 times. Thereafter, the extraction liquid was concentrated, thereby obtaining 198 g of an objective compound (compound (11)) in the form of a colorless liquid (yield: 97%, GC purity: 99%).

The results of instrumental analysis of the obtained compound (11) were as follows.

¹-NMR: 1.58 (d,J=12.5 Hz,2H), 1.63 (s,3H),1.71-1.89 (m,8H), 1.98 (s,3H), 2.00 (m,2H), 2.30 (m,2H), 4.62 (s,2H), 4.80 (s,2H), 5.66 (m,1H), 6.23 (m,1H)

¹³C-NMR: 18.04, 22.15, 26.42, 27.14, 32.82, 34.38, 36.11, 37.92, 60.44, 61.28, 89.42, 126.79, 135.18, 165.61, 166.30, 167.20

GC-MS: 350 (M+,1.4%), 206 (0.13%), 149 (47%), 148 (100%), 133 (20%), 69 (37%)

Monomer Synthesis Example 3 Synthesis of Compound (12)

The compound (12) used in the polymer synthesis examples described later was synthesized by a method described in paragraph [0070] of WO 2007/94473.

Polymer Synthesis Example 1

In a three-necked flask equipped with a thermometer and a reflux tube, 11.68 g (68.68 mmol) of a compound (1), 15.00 g (51.02 mmol) of a compound (2), 16.45 g (62.79 mmol) of a compound (3), 4.62 g (27.47 mmol) of a compound (4) and 3.24 g (13.74 mmol) of a compound (5) were dissolved in 76.49 g of methyl ethyl ketone (MEK) to obtain a solution. Then, 20.13 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 42.49 g of MEK heated to 78° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of an n-heptane/isopropylalcohol mixed solvent, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 30.82 g of a polymeric compound 1 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 9,900, and the dispersity was 1.45. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o/p=36.3/25.6/16.8/13.4/7.9.

Polymer Synthesis Example 2

In a three-necked flask equipped with a thermometer and a reflux tube, 12.52 g (73.67 mmol) of a compound (1), 13.95 g (47.47 mmol) of a compound (2), 17.91 g (68.36 mmol) of a compound (3) and 4.78 g (28.48 mmol) of a compound (4) were dissolved in 73.85 g of methyl ethyl ketone (MEK) to obtain a solution. Then, 21.8 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 40.96 g of MEK heated to 78° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of n-heptane, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 34 g of a polymeric compound 2 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,700, and the dispersity was 1.65. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o=38.2/28.5/21.0/12.3.

Polymer Synthesis Example 3

In a three-necked flask equipped with a thermometer and a reflux tube, 11.00 g (64.73 mmol) of a compound (1), 13.95 g (47.47 mmol) of a compound (2), 37.31 g (142.41 mmol) of a compound (3) and 5.09 g (21.58 mmol) of a compound (5) were dissolved in 101.04 g of methyl ethyl ketone (MEK) to obtain a solution. Then, 27.6 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 56.11 g of MEK heated to 78° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of n-heptane, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 33 g of a polymeric compound 2 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,300, and the dispersity was 1.68. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o=33.1/24.9/32.0/10.0.

Polymer Synthesis Example 4

In a three-necked flask equipped with a thermometer and a reflux tube, 11.00 g (64.73 mmol) of a compound (1), 13.95 g (47.47 mmol) of a compound (2), 12.69 g (75.52 mmol) of a compound (4) and 5.09 g (21.58 mmol) of a compound (5) were dissolved in 64.11 g of methyl ethyl ketone (MEK) to obtain a solution. Then, 20.9 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 35.60 g of MEK heated to 78° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of n-heptane, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 31 g of a polymeric compound 4 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,800, and the dispersity was 1.63. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o=32.9/24.8/32.1/10.2.

Polymer Synthesis Example 5

In a three-necked flask equipped with a thermometer and a reflux tube, 15.37 g (69.23 mmol) of a compound (6), 13.95 g (47.47 mmol) of a compound (2), 16.58 g (63.29 mmol) of a compound (3), 4.65 g (27.69 mmol) of a compound (4) and 3.27 g (13.85 mmol) of a compound (5) were dissolved in 80.74 g of methyl ethyl ketone (MEK) to obtain a solution. Then, 22.2 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 44.84 g of MEK heated to 78° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of n-heptane, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 37 g of a polymeric compound 5 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,600, and the dispersity was 1.70. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o/p=35.1/26.4/18.2/13.4/6.9.

Polymer Synthesis Example 6

In a three-necked flask equipped with a thermometer and a reflux tube, 15.37 g (69.23 mmol) of a compound (6), 13.95 g (47.47 mmol) of a compound (2), 12.75 g (51.43 mmol) of a compound (7), 4.65 g (27.69 mmol) of a compound (4) and 3.27 g (13.85 mmol) of a compound (5) were dissolved in 75.00 g of methyl ethyl ketone (MEK) to obtain a solution. Then, 20.9 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 41.65 g of MEK heated to 78° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of n-heptane, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 35 g of a polymeric compound 6 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,500, and the dispersity was 1.60. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o/p=34.3/25.7/19.5/12.9/7.6.

Polymer Synthesis Example 7

In a three-necked flask equipped with a thermometer and a reflux tube, 16.02 g (72.15 mmol) of a compound (6), 13.95 g (47.47 mmol) of a compound (2), 17.91 g (68.36 mmol) of a compound (3) and 4.78 g (28.48 mmol) of a compound (4) were dissolved in 79.00 g of methyl ethyl ketone (MEK) to obtain a solution. Then, 21.7 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 43.88 g of MEK heated to 78° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of n-heptane, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 26 g of a polymeric compound 7 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,100, and the dispersity was 1.65. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o=37.5/28.3/21.1/13.1.

Polymer Synthesis Example 8

In a three-necked flask equipped with a thermometer and a reflux tube, 14.37 g (64.73 mmol) of a compound (6), 13.95 g (47.47 mmol) of a compound (2), 37.31 g (142.41 mmol) of a compound (3) and 5.09 g (21.58 mmol) of a compound (5) were dissolved in 106.09 g of methyl ethyl ketone (MEK) to obtain a solution. Then, 27.6 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 58.92 g of MEK heated to 78° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of n-heptane, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 35 g of a polymeric compound 8 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,000, and the dispersity was 1.62.

Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o=33.2/25.3/31.4/10.1.

Polymer Synthesis Example 9

In a three-necked flask equipped with a thermometer and a reflux tube, 14.37 g (64.73 mmol) of a compound (6), 13.95 g (47.47 mmol) of a compound (2), 12.69 g (75.52 mmol) of a compound (4) and 5.09 g (21.58 mmol) of a compound (5) were dissolved in 69.16 g of methyl ethyl ketone (MEK) to obtain a solution. Then, 20.9 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 38.41 g of MEK heated to 78° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of n-heptane, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 32 g of a polymeric compound 9 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,600, and the dispersity was 1.67. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o=33.0/25.1/32.1/9.8.

Polymer Synthesis Example 10

In a three-necked flask equipped with a thermometer and a reflux tube, 17.72 g (63.29 mmol) of a compound (8), 13.95 g (47.47 mmol) of a compound (2), 16.58 g (63.29 mmol) of a compound (3), 4.65 g (27.69 mmol) of a compound (4) and 3.27 g (13.85 mmol) of a compound (5) were dissolved in 84.26 g of methyl ethyl ketone (MEK) to obtain a solution. Then, 25.9 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 46.81 g of MEK heated to 78° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of n-heptane, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 39 g of a polymeric compound 10 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,900, and the dispersity was 1.63. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o/p=35.1/26.2/18.2/13.7/6.8.

Polymer Synthesis Example 11

In a three-necked flask equipped with a thermometer and a reflux tube, 17.85 g (63.29 mmol) of a compound (9), 13.95 g (47.47 mmol) of a compound (2), 16.58 g (63.29 mmol) of a compound (3), 4.65 g (27.69 mmol) of a compound (4) and 3.27 g (13.85 mmol) of a compound (5) were dissolved in 84.46 g of gamma-butyrolactone (GBL) to obtain a solution. Then, 25.9 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 46.91 g of GBL heated to 80° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of a methanol/water mixed solvent, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 39 g of a polymeric compound 11 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,500, and the dispersity was 1.68. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o/p=35.3/26.6/18.2/13.6/6.3.

Polymer Synthesis Example 12

In a three-necked flask equipped with a thermometer and a reflux tube, 14.62 g (65.27 mmol) of a compound (10), 13.95 g (47.47 mmol) of a compound (2), 16.58 g (63.29 mmol) of a compound (3), 4.65 g (27.69 mmol) of a compound (4) and 3.27 g (13.85 mmol) of a compound (5) were dissolved in 79.62 g of gamma-butyrolactone (GBL) to obtain a solution. Then, 26.1 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 44.21 g of GBL heated to 80° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of a methanol/water mixed solvent, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 37 g of a polymeric compound 12 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,700, and the dispersity was 1.67. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o/p=35.6/26.2/18.1/13.5/6.6.

Polymer Synthesis Example 13

In a three-necked flask equipped with a thermometer and a reflux tube, 15.31 g (68.36 mmol) of a compound (10), 13.95 g (47.47 mmol) of a compound (2), 17.91 g (68.36 mmol) of a compound (3) and 4.78 g (28.48 mmol) of a compound (4) were dissolved in 77.94 g of gamma-butyrolactone (GBL) to obtain a solution. Then, 25.5 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 43.28 g of GBL heated to 80° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of a methanol/water mixed solvent, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 36 g of a polymeric compound 13 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,300, and the dispersity was 1.66. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o=37.9/28.3/21.0/12.8.

Polymer Synthesis Example 14

In a three-necked flask equipped with a thermometer and a reflux tube, 14.50 g (64.73 mmol) of a compound (10), 13.95 g (47.47 mmol) of a compound (2), 37.31 g (142.41 mmol) of a compound (3) and 5.09 g (21.58 mmol) of a compound (5) were dissolved in 106.92 g of gamma-butyrolactone (GBL) to obtain a solution. Then, 27.6 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 59.03 g of GBL heated to 80° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of a methanol/water mixed solvent, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 35 g of a polymeric compound 14 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,600, and the dispersity was 1.64. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o=33.1/25.4/31.3/10.2.

Polymer Synthesis Example 15

In a three-necked flask equipped with a thermometer and a reflux tube, 14.50 g (64.73 mmol) of a compound (10), 13.95 g (47.47 mmol) of a compound (2), 12.69 g (75.52 mmol) of a compound (4) and 5.09 g (21.58 mmol) of a compound (5) were dissolved in 69.36 g of gamma-butyrolactone (GBL) to obtain a solution. Then, 25.1 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 38.51 g of GBL heated to 80° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of n-heptane, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 32 g of a polymeric compound 15 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,900, and the dispersity was 1.62. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o=32.9/24.8/32.6/9.7.

Polymer Synthesis Example 16

In a three-necked flask equipped with a thermometer and a reflux tube, 18.74 g (66.46 mmol) of a compound (9), 13.95 g (47.47 mmol) of a compound (2), 17.91 g (68.36 mmol) of a compound (3) and 4.78 g (28.48 mmol) of a compound (4) were dissolved in 83.08 g of gamma-butyrolactone (GBL). Then, 21.7 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 46.14 g of GBL heated to 80° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of n-heptane, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 38 g of a polymeric compound 16 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,500, and the dispersity was 1.67. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o=38.0/27.8/20.8/13.4.

Polymer Synthesis Example 17

In a three-necked flask equipped with a thermometer and a reflux tube, 18.25 g (64.73 mmol) of a compound (9), 13.95 g (47.47 mmol) of a compound (2), 37.31 g (142.41 mmol) of a compound (3) and 5.09 g (21.58 mmol) of a compound (5) were dissolved in 111.91 g of gamma-butyrolactone (GBL) to obtain a solution. Then, 33.1 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 62.16 g of GBL heated to 80° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of a methanol/water mixed solvent, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 37 g of a polymeric compound 17 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,200, and the dispersity was 1.67. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o=33.5/25.4/31.0/10.1.

Polymer Synthesis Example 18

In a three-necked flask equipped with a thermometer and a reflux tube, 18.25 g (64.73 mmol) of a compound (9), 13.95 g (47.47 mmol) of a compound (2), 12.69 g (75.52 mmol) of a compound (4) and 5.09 g (21.58 mmol) of a compound (5) were dissolved in 74.98 g of gamma-butyrolactone (GBL) to obtain a solution. Then, 25.1 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 41.64 g of GBL heated to 80° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of a methanol/water mixed solvent, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 35 g of a polymeric compound 18 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,600, and the dispersity was 1.62. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o=33.3/24.7/33.1/8.9.

Polymer Synthesis Example 19

In a three-necked flask equipped with a thermometer and a reflux tube, 18.61 g (66.46 mmol) of a compound (8), 13.95 g (47.47 mmol) of a compound (2), 17.91 g (68.36 mmol) of a compound (3) and 4.78 g (28.48 mmol) of a compound (4) were dissolved in 82.89 g of methyl ethyl ketone (MEK) to obtain a solution. Then, 21.7 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 46.03 g of MEK heated to 78° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of n-heptane, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 38 g of a polymeric compound 19 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,300, and the dispersity was 1.66. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o=38.1/28.2/20.1/13.6.

Polymer Synthesis Example 20

In a three-necked flask equipped with a thermometer and a reflux tube, 18.12 g (64.73 mmol) of a compound (8), 13.95 g (47.47 mmol) of a compound (2), 37.31 g (142.41 mmol) of a compound (3) and 5.09 g (21.58 mmol) of a compound (5) were dissolved in 111.72 g of methyl ethyl ketone (MEK) to obtain a solution. Then, 33.1 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 62.05 g of MEK heated to 80° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of n-heptane, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 52 g of a polymeric compound 20 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,000, and the dispersity was 1.67. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o=33.5/25.3/30.9/10.3.

Polymer Synthesis Example 21

In a three-necked flask equipped with a thermometer and a reflux tube, 18.12 g (64.73 mmol) of a compound (8), 13.95 g (47.47 mmol) of a compound (2), 12.69 g (75.52 mmol) of a compound (4) and 5.09 g (21.58 mmol) of a compound (5) were dissolved in 74.79 g of methyl ethyl ketone (MEK) to obtain a solution. Then, 25.1 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 41.53 g of MEK heated to 80° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of a methanol/water mixed solvent, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 35 g of a polymeric compound 21 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,800, and the dispersity was 1.67. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o=33.2/24.7/32.8/9.3.

Polymer Synthesis Example 22

In a three-necked flask equipped with a thermometer and a reflux tube, 7.85 g (46.16 mmol) of a compound (1), 9.31 g (31.65 mmol) of a compound (2), 8.50 g (34.29 mmol) of a compound (7), 3.10 g (18.46 mmol) of a compound (4) and 2.18 g (9.23 mmol) of a compound (5) were dissolved in 45.85 g of methyl ethyl ketone (MEK) to obtain a solution. Then, 14.0 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 25.47 g of MEK heated to 78° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of n-heptane, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with an n-heptane/isopropylalcohol mixed solvent and drying, thereby obtaining 21 g of a polymeric compound 22 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,700, and the dispersity was 1.53.

Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o/p=34.7/26.2/19.1/12.5/7.5.

Polymer Synthesis Example 23

In a three-necked flask equipped with a thermometer and a reflux tube, 19.97 g (67.94 mmol) of a compound (2), 12.36 g (35.33 mmol) of a compound (11), 20.00 g (108.70 mmol) of a compound (12) and 11.54 g (48.92 mmol) of a compound (5) were dissolved in 94.61 g of propylene glycol methyl ether acetate (PM). Then, 26.1 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 52.55 g of PM heated to 80° C. in a nitrogen atmosphere over 6 hours.

Thereafter, the reaction solution was heated for 1 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of a methanol/water mixed solvent, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with a methanol/water mixed solvent and drying, thereby obtaining 44 g of a polymeric compound 23 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 10,500, and the dispersity was 1.47.

Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o=28.0/14.2/36.0/21.8.

Polymer Synthesis Example 24

In a three-necked flask equipped with a thermometer and a reflux tube, 12.82 g (43.62 mmol) of a compound (2), 5.10 g (17.45 mmol) of a compound (13), 80.00 g (305.34 mmol) of a compound (3) and 4.12 g (17.45 mmol) of a compound (5) were dissolved in 152.28 g of propylene glycol methyl ether acetate (PM). Then, 15.4 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 84.60 g of PM heated to 80° C. in a nitrogen atmosphere over 3 hours.

Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of n-heptane, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with a methanol/n-heptane mixed solvent and drying, thereby obtaining 23 g of a polymeric compound 24 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 6,400, and the dispersity was 1.29. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o=28.1/9.5/47.6/14.8.

Polymer Synthesis Example 25

In a three-necked flask equipped with a thermometer and a reflux tube, 10.13 g (34.46 mmol) of a compound (2), 4.53 g (15.51 mmol) of a compound (13), 20.00 g (108.54 mmol) of a compound (12) and 3.66 g (15.51 mmol) of a compound (5) were dissolved in 56.87 g of propylene glycol methyl ether acetate (PM). Then, 17.4 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 31.59 g of PM heated to 80° C. in a nitrogen atmosphere over 6 hours.

Thereafter, the reaction solution was heated for 1 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of n-heptane, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with a 2-propanol/n-heptane mixed solvent and drying, thereby obtaining 27 g of a polymeric compound 25 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 9,700, and the dispersity was 1.65. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o=22.4/9.1/56.8/11.7.

Polymer Synthesis Example 26

In a three-necked flask equipped with a thermometer and a reflux tube, 9.30 g (31.65 mmol) of a compound (2), 9.10 g (38.88 mmol) of a compound (14) and 4.05 g (17.18 mmol) of a compound (5) were dissolved in 33.12 g of methyl ethyl ketone (MEK) to obtain a solution. Then, 5.8 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 18.40 g of MEK heated to 78° C. in a nitrogen atmosphere over 6 hours. Thereafter, the reaction solution was heated for 1 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of a methanol/water mixed solvent, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with a methanol/water mixed solvent and drying, thereby obtaining 15 g of a polymeric compound 26 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 9,100, and the dispersity was 1.53. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n=39.7/41.2/19.1.

Polymer Synthesis Example 27

In a three-necked flask equipped with a thermometer and a reflux tube, 9.30 g (31.65 mmol) of a compound (2), 6.53 g (38.88 mmol) of a compound (4) and 4.05 g (17.18 mmol) of a compound (5) were dissolved in 29.27 g of methyl ethyl ketone (MEK) to obtain a solution. Then, 7.0 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 16.25 g of MEK heated to 78° C. in a nitrogen atmosphere over 6 hours. Thereafter, the reaction solution was heated for 1 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of a methanol/water mixed solvent, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with a methanol/water mixed solvent and drying, thereby obtaining 14 g of a polymeric compound 27 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 9,400, and the dispersity was 1.51. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n=39.5/41.0/19.5.

Polymer Synthesis Example 28

In a three-necked flask equipped with a thermometer and a reflux tube, 12.82 g (43.62 mmol) of a compound (2), 80.00 g (305.34 mmol) of a compound (3), 2.93 g (17.45 mmol) of a compound (4) and 4.12 g (17.45 mmol) of a compound (5) were dissolved in 149.81 g of methyl ethyl ketone (MEK) to obtain a solution. Then, 15.4 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 83.22 g of MEK heated to 80° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of n-heptane, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with a methanol/n-heptane mixed solvent and drying, thereby obtaining 25 g of a polymeric compound 28 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 6,300, and the dispersity was 1.41. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o=27.4/48.6/9.7/14.3.

Comparative Polymer Synthesis Example 1

In a three-necked flask equipped with a thermometer and a reflux tube, 10.29 g (43.62 mmol) of a compound (15), 80.00 g (305.34 mmol) of a compound (3), 2.93 g (17.45 mmol) of a compound (4) and 4.12 g (17.45 mmol) of a compound (5) were dissolved in 146.01 g of methyl ethyl ketone (MEK) to obtain a solution. Then, 15.4 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 81.12 g of MEK heated to 80° C. in a nitrogen atmosphere over 3 hours. Thereafter, the reaction solution was heated for 4 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of n-heptane, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with a methanol/n-heptane mixed solvent and drying, thereby obtaining 25 g of a polymeric compound 29 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 6,300, and the dispersity was 1.41. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n/o=27.4/48.6/9.7/14.3.

Comparative Polymer Synthesis Example 2

In a three-necked flask equipped with a thermometer and a reflux tube, 7.47 g (31.65 mmol) of a compound (15), 9.10 g (38.88 mmol) of a compound (14) and 4.05 g (17.18 mmol) of a compound (5) were dissolved in 30.93 g of methyl ethyl ketone (MEK) to obtain a solution. Then, 5.8 mmol of dimethyl 2,2′-azobis(isobutyrate) (product name: V-601, manufactured by Wako Pure Chemical Industries, Ltd.) was added and dissolved in the obtained solution.

The resultant was dropwise added to 17.18 g of MEK heated to 78° C. in a nitrogen atmosphere over 6 hours. Thereafter, the reaction solution was heated for 1 hour while stirring, and then cooled to room temperature.

The obtained reaction polymer solution was dropwise added to an excess amount of a methanol/water mixed solvent, and an operation to deposit a polymer was conducted. Thereafter, the precipitated white powder was separated by filtration, followed by washing with a methanol/water mixed solvent and drying, thereby obtaining 14 g of a polymeric compound 30 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 8,900, and the dispersity was 1.51. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m/n=39.8/41.2/19.0.

Polymer Synthesis Example 29

The same procedure as in the aforementioned polymer synthesis examples was performed, except that the compound (2′) and the compound (16) were used in predetermined molar ratio, thereby obtaining a polymeric compound 31 as an objective compound.

With respect to the obtained polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 7,300, and the dispersity was 1.6. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m=50/50.

Measurement of Receding Angle

100 parts by weight of each of the polymeric compounds 1, 5, 10 to 12 and 28 was individually dissolved in 2,500 parts by weight of a PGMEA/PGME mixed solvent (weight ratio: PGMEA/PGME=6/4), thereby obtaining a resin solution. Then, using a spinner, each of the resin solutions was applied onto an 8-inch silicon wafer that had been treated with hexamethyldisilazane (HMDS), and the solution was then prebaked (PAB) and dried on a hotplate at 110° C. for 60 seconds, thus forming a resin film with a film thickness of 120 nm.

A water droplet was dripped onto the surface of each resin film, and a DROP MASTER-700 apparatus (a product name, manufactured by Kyowa Interface Science Co. Ltd.) was used to measure the receding angle (receding angle measurement: water 50 μl). The measured value was defined as the “receding angle (°) prior to development”. Subsequently, the wafer which had been subjected to the measurement of contact angle was subjected to an alkali developing treatment for 30 seconds at 23° C. in a 2.38% by weight aqueous solution of tetramethylammonium hydroxide (TMAH), and the receding angle was measured in the same manner as described above. The measured value was defined as the “receding angle (°) after 30 seconds development”. The results are shown in Table 1.

TABLE 1 Receding angle Receding angle after 30 prior to seconds Δ Receding development development angle (°) (°) (°) Polymeric compound 1 55.0 32.1 22.9 Polymeric compound 5 54.3 36.8 17.5 Polymeric compound 10 54.1 37.1 17.0 Polymeric compound 11 54.9 31.8 23.1 Polymeric compound 12 54.5 32.3 22.2 Polymeric compound 28 65.6 50.6 15.0

From the results shown above, it was found that, when the resin contained both of the structural unit (a0) and the structural unit (a2), the hydrophilicity thereof changed significantly by coming in contact with an alkali developing solution, and it was confirmed that the hydrophilicity of the film surface became significantly high after 30 seconds development. These results show that generation of defects following development caused by high water repellency of the resist film surface can be reduced.

Examples 1 to 28, Comparative Examples 1 and 2

100 parts by weight of the component (A) shown in Table 2, 9.8 parts by weight of a compound represented by chemical formula (B)-1 shown below, 0.4 parts by weight of tri-n-pentylamine, 10 parts by weight of γ-butyrolactone and 2,500 parts by weight of a PGMEA/PGME mixed solvent (PGMEA/PGME=6/4 (weight ratio)) were mixed together and dissolved to obtain a positive resist composition.

Using the obtained resist compositions, the following evaluations were conducted.

(Formation of Resist Pattern)

An organic anti-reflection film composition (product name: ARC95, manufactured by Brewer Science Ltd.) was applied onto an 12-inch silicon wafer using a spinner, and the composition was then baked at 205° C. for 60 seconds, thereby forming an organic anti-reflection film having a film thickness of 89 nm. Then, each of the resist compositions obtained above was applied onto the anti-reflection film using a spinner, and was then prebaked (PAB) on a hotplate at a temperature indicated in Table 2 for 60 seconds and dried, thereby forming a resist film having a film thickness of 100 nm.

Subsequently, a coating solution for forming a protection film (product name: TILC-057; manufactured by Tokyo Ohka Kogyo Co., Ltd.) was applied onto the resist film using a spinner, and then heated at 90° C. for 60 seconds, thereby forming a top coat with a film thickness of 35 nm.

Thereafter, using an ArF exposure apparatus for immersion lithography (product name: NSR-S609B, manufactured by Nikon Corporation, NA (numerical aperture)=1.07, 2/3 annular illumination, reduction ratio: 1/4, immersion medium: water), the resist film having a top coat formed thereon was selectively irradiated with an ArF excimer laser (193 nm) through a mask pattern targeting a contact hole pattern with a hole diameter of 90 nm and a pitch of 140 nm (hereafter, this contact hole pattern is referred to as “CH pattern”).

Next, a post exposure bake (PEB) treatment was conducted at a temperature indicated in Table 2 for 60 seconds, followed by development for 60 seconds at 23° C. in a 2.38% by weight aqueous solution of tetramethylammonium hydroxide (TMAH) (product name: NMD-3; manufactured by Tokyo Ohka Kogyo Co., Ltd.). Then, the resist film was rinsed for 30 seconds with pure water, followed by drying by shaking.

As a result, in each of the examples, a CH pattern was formed.

(Evaluation of Pattern Shape)

Each of the CH patterns formed in the (Formation of resist pattern) was observed from the upper side thereof using a scanning electron microscope (SEM), and the circularity was evaluated with the following criteria.

The results are shown in Table 2.

A: no unevenness was observed at the circumferential portions of the hole pattern, and the pattern shape was excellent

B: unevenness was observed at some circumferential portions of the hole pattern

C: a part of the circumferential portion of the hole pattern was distorted

D: the entire circumferential portion of the hole pattern was distorted

TABLE 2 Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Component Polymeric Polymeric Polymeric Polymeric Polymeric Polymeric (A) compound 1 compound 2 compound 3 compound 4 compound 5 compound 6 PAB/PEB 90/85 90/85 90/85 110/110 90/85 100/95  [° C.] Circularity A A B B A A Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Component Polymeric Polymeric Polymeric Polymeric Polymeric Polymeric (A) compound 7 compound 8 compound 9 compound 10 compound 11 compound 12 PAB/PEB 90/85 90/85 110/110 90/85 90/85 90/85 [° C.] Circularity A B B A A A Ex. 13 Ex. 14 Ex. 15 Ex. 16 Ex. 17 Ex. 18 Component Polymeric Polymeric Polymeric Polymeric Polymeric Polymeric (A) compound 13 compound 14 compound 15 compound 16 compound 17 compound 18 PAB/PEB 90/85 90/85 110/110 90/85 90/85 110/110 [° C.] Circularity A B B A B B Ex. 19 Ex. 20 Ex. 21 Ex. 22 Ex. 23 Ex. 24 Component Polymeric Polymeric Polymeric Polymeric Polymeric Polymeric (A) compound 19 compound 20 compound 21 compound 22 compound 23 compound 24 PAB/PEB 90/85 90/85 110/110 100/95  110/110 90/85 [° C.] Circularity A B B A A A Ex. 25 Ex. 26 Ex. 27 Ex. 28 Comp. Ex. 1 Comp. Ex. 2 Component Polymeric Polymeric Polymeric Polymeric Polymeric Polymeric (A) compound 25 compound 26 compound 27 compound 28 compound 29 compound 30 PAB/PEB 110/110 110/110 110/110 90/85 90/85 110/110 [° C.] Circularity A B B A C D

As seen from the results, the resist patterns formed using the resist compositions of Examples 1 to 28 had an excellent shape.

Example 29

The components shown in Table 3 below, γ-butyrolactone (10 parts by weight) and a mixed solvent of PGMEA and PGME (PGMEA/PGME=6/4 (weight ratio)) (2,500 parts by weight) were mixed together and dissolved to obtain a positive resist composition.

TABLE 3 Component Component Component Other (A) (B) (D) additive Ex. 29 (A)-29 (B)-2 (B)-3 (D)-2 (F)-1 [100] [9.5] [2.0] [0.6] [1.5]

In Table 3, the reference characters indicate the following. Further, the values in brackets [ ] indicate the amount (in terms of parts by weight) of the component added.

(A)-29: the aforementioned polymeric compound 31

(B)-2: a compound represented by formula (B)-2 shown below

(B)-3: a compound represented by formula (B)-3 shown below

(D)-2: 1,8-naphthalenediamine

(F)-1: a fluorine-containing polymeric compound represented by formula (F)-1 shown below. Mw=25,000, Mw/Mn=1.5, compositional ratio of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula): l/m=80/20

Using the obtained resist compositions, resist patterns were formed in the following manner, and evaluations were performed as follows.

An organic anti-reflection film composition (product name: ARC29A, manufactured by Brewer Science Ltd.) was applied onto an 8-inch silicon wafer using a spinner, and the composition was then baked at 205° C. for 60 seconds, thereby forming an organic anti-reflection film having a film thickness of 77 nm. Then, the resist composition was applied onto the anti-reflection film using a spinner, and was then prebaked (PAB) on a hotplate at 120° C. for 60 seconds and dried, thereby forming a resist film having a film thickness of 100 nm.

Subsequently, the resist film was selectively irradiated with an ArF excimer laser (193 nm) through a mask pattern, using an ArF exposure apparatus NSR-S302A (manufactured by Nikon Corporation; NA (numerical aperture)=0.6, annu.). Thereafter, a post exposure bake (PEB) treatment was conducted at 95° C. for 60 seconds, followed by alkali development for 30 seconds at 23° C. in a 2.38% by weight aqueous solution of tetramethylammonium hydroxide (TMAH) (product name: NMD-3; manufactured by Tokyo Ohka Kogyo Co., Ltd.). Then, the resist was washed for 25 seconds with pure water, followed by drying by shaking.

As a result, a line and space pattern (L/S pattern) in which lines having a line width of 130 nm were arranged at equal intervals (pitch: 260 nm) was formed on the resist film. The optimum exposure dose Eop (mJ/cm²; sensitivity) for forming the L/S pattern was found to be 41 mJ/cm². Further, the cross-sectional shape of the obtained L/S pattern was observed using a scanning electron microscope (SEM) (product name: SEM S-9220, manufactured by Hitachi, Ltd.). As a result, it was found that the pattern exhibited an excellent rectangularity.

[Synthesis of Fluorine-Containing Polymeric Compound (F)-1]

The aforementioned (F)-1 was synthesized as follows.

(1. Synthesis of Compound (f111))

61 g (600 mmol) of triethylamine and 64 g (418 mmol) of methyl bromoacetate were added to 300 ml of a THF solution containing 30 g (348 mmol) of methacrylic acid in a nitrogen atmosphere at 0° C., and the temperature was elevated to room temperature, followed by stirring for 3 hours. After conducting thin-layer chromatography to confirm that the raw materials had been consumed, the reaction solution was subjected to distillation under reduced pressure to remove the solvent. Then, water was added to the resultant, and extraction was conducted with ethyl acetate three times. The resulting organic phase was washed with water twice, and then subjected to distillation under reduced pressure to remove the solvent, thereby obtaining 47 g of a compound (21)-1 in the form of a colorless liquid (yield: 85%).

Subsequently, 700 ml of a THF solution containing 30 g (190 mmol) of the compound (21)-1 was prepared, and 700 ml of a 2.38% by weight aqueous solution of TMAH was added thereto, followed by stirring at room temperature for 3 hours. After conducting thin-layer chromatography to confirm that the raw materials had been consumed, THF was distilled off under reduced pressure. Then, the resulting aqueous reaction solution was cooled to 0° C., and 50 ml of a 10N hydrochloric acid was added thereto to render the aqueous reaction solution acidic, followed by extraction with ethyl acetate three times. The resulting organic phase was washed with water twice, and the solvent was distilled off under reduced pressure, thereby obtaining 26 g of a compound (21)-2 in the form of a colorless liquid (yield: 95%).

Next, 26 g (180.39 mmol) of the compound (21)-2 was added to 200 ml of a THF solution containing 23.48 g (234.5 mmol) of 2,2,2-trifluoroethanol (CF₃CH₂OH), 51.9 g (270.6 mmol) of ethyldiisopropylaminocarbodiimide hydrochloride (EDCl) and 0.11 g (0.9 mmol) of dimethylaminopyridine (DMAP) in a nitrogen atmosphere at 0° C., and the temperature was elevated to room temperature, followed by stirring for 3 hours. After conducting thin-layer chromatography to confirm that the raw materials had been consumed, the reaction solution was cooled to 0° C., and water was added thereto to stop the reaction. Then, extraction was conducted with ethyl acetate three times, and the obtained organic phase was washed with water twice. Thereafter, the solvent was distilled off under reduced pressure to obtain a crude product, and the obtained crude product was purified by silica gel filtration (using ethyl acetate), thereby obtaining 25 g of the objective compound (f111) in the form of a colorless liquid.

The obtained compound (f111) was analyzed by ¹H-NMR to confirm its structure.

The results of the ¹H-NMR analysis are shown below.

¹H-NMR(CDCl₃,400 MHz): δ(ppm)=6.24 (s,1H,Hb), 5.70 (s,1H,Hb), 4.80 (s,2H,Hc), 4.60-4.51 (m,2H,Hd), 1.99 (s,3H,Ha)

(2. Synthesis of (F)-1)

15.00 g (54.32 mmol) of the compound (f111) and 5.21 g (23.28 mmol) of the compound (f211) were added to a three-necked flask equipped with a thermometer and a reflux tube and were dissolved by adding 114.52 g of THF thereto. Then, 4.66 mmol of dimethyl 2,2′-azobis(isobutyrate) (V-601) was added and dissolved in the obtained solution. The solution was stirred while heating at 80° C. for 6 hours in a nitrogen atmosphere, and was then cooled to room temperature. The resulting polymer solution was concentrated under reduced pressure, and dropwise added to an excess amount of n-heptane to thereby precipitate a polymer. Then, the precipitated polymer was separated by filtration, followed by washing and drying, thereby obtaining 5.6 g of a fluorine-containing polymeric compound (F)-1 as an objective compound.

With respect to the obtained fluorine-containing polymeric compound, the weight average molecular weight (Mw) and the dispersity (Mw/Mn) were determined by the polystyrene equivalent value as measured by gel permeation chromatography (GPC). As a result, it was found that the weight average molecular weight was 25,000, and the dispersity was 1.5. Further, as a result of an analysis by carbon 13 nuclear magnetic resonance spectroscopy (600 MHz, ¹³C-NMR), it was found that the composition of the copolymer (ratio (molar ratio) of the respective structural units within the structural formula) was l/m=80/20.

While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims. 

1. A positive resist composition comprising a base component (A) which exhibits increased solubility in an alkali developing solution under action of acid and an acid-generator component (B) which generates acid upon exposure, said component (A) comprising: a polymeric compound (A1′) comprising a structural unit (a0) represented by general formula (a0-1) shown below and a structural unit (a2) derived from an acrylate ester containing a lactone-containing cyclic group exclusive of said structural unit (a0), said polymeric compound (A1′) containing an acid dissociable, dissolution inhibiting group within the structure thereof; or a polymeric compound (A1) comprising a structural unit (a0) represented by general formula (a0-1) shown below and a structural unit (a1) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group exclusive of said structural unit (a0) and said structural unit (a2):

wherein R¹ represents a hydrogen atom, a lower alkyl group or a halogenated lower alkyl group; R² represents a divalent linking group; each R′ independently represents a hydrogen atom, an alkyl group of 1 to 6 carbon atoms, an alkoxy group of 1 to 6 carbon atoms or —COOR″, wherein R″ represents a hydrogen atom or an alkyl group; and A″ represents an oxygen atom, a sulfur atom, or an alkylene group of 1 to 5 carbon atoms which may contain an oxygen atom or a sulfur atom.
 2. The positive resist composition according to claim 1, wherein said structural unit (a1) comprises at least two types of structural units.
 3. The positive resist composition according to claim 1, wherein said structural unit (a1) comprises at least one member selected from the group consisting of a structural unit represented by general formula (a1-0-11) shown below, a structural unit represented by general formula (a1-0-12) shown below and a structural unit represented by general formula (a1-0-2) shown below:

wherein R represents a hydrogen atom, a lower alkyl group or a halogenated lower alkyl group; R²¹ represents an alkyl group; R²² represents a group which forms an aliphatic monocyclic group with the carbon atom to which R²² is bonded; R²³ represents a branched alkyl group; R²⁴ represents a group which forms an aliphatic polycyclic group with the carbon atom to which R²⁴ is bonded; Y² represents a divalent linking group; and X² represents an acid dissociable, dissolution inhibiting group.
 4. The positive resist composition according to claim 1, wherein the total amount of said structural unit (a0) and said structural unit (a2) within said polymeric compound (A1′) is 5 to 70 mol %.
 5. The positive resist composition according to claim 1, wherein said structural unit (a2) comprises at least one member selected from the group consisting of a structural unit represented by general formula (a2-1) shown below and a structural unit represented by general formula (a2-2) shown below:

wherein R represents a hydrogen atom, a lower alkyl group or a halogenated lower alkyl group; each R′ independently represents a hydrogen atom, an alkyl group of 1 to 5 carbon atoms, an alkoxy group of 1 to 5 carbon atoms or —COOR″, wherein R″ represents a hydrogen atom or an alkyl group; R²⁹ represents a single bond or a divalent linking group; s″ represents an integer of 0 to 2; and A″ represents an oxygen atom, a sulfur atom or an alkylene group of 1 to 5 carbon atoms which may contain an oxygen atom or a sulfur atom.
 6. The positive resist composition according to claim 1, wherein said polymeric compound (A1′) further comprises said structural unit (a1).
 7. The positive resist composition according to claim 1, wherein said polymeric compound (A1) or said polymeric compound (A1′) further comprises a structural unit (a3) derived from an acrylate ester containing a polar group-containing aliphatic hydrocarbon group.
 8. The positive resist composition according to claim 1, which further comprises a nitrogen-containing organic compound (D).
 9. A method of forming a resist pattern, comprising: applying a positive resist composition of claim 1 to a substrate to form a resist film on the substrate; conducting exposure of said resist film; and alkali-developing said resist film to form a resist pattern.
 10. A polymeric compound comprising: a component (A1′) comprising a structural unit (a0) represented by general formula (a0-1) shown below and a structural unit (a2) derived from an acrylate ester containing a lactone-containing cyclic group exclusive of said structural unit (a0), said component (A1′) containing an acid dissociable, dissolution inhibiting group within the structure thereof; or a component (A1) comprising a structural unit (a0) represented by general formula (a0-1) shown below and a structural unit (a1) derived from an acrylate ester containing an acid dissociable, dissolution inhibiting group exclusive of said structural unit (a0) and said structural unit (a2):

wherein R¹ represents a hydrogen atom, a lower alkyl group or a halogenated lower alkyl group; R² represents a divalent linking group; each R′ independently represents a hydrogen atom, an alkyl group of 1 to 6 carbon atoms, an alkoxy group of 1 to 6 carbon atoms or —COOR″, wherein R″ represents a hydrogen atom or an alkyl group; and A″ represents an oxygen atom, a sulfur atom, or an alkylene group of 1 to 5 carbon atoms which may contain an oxygen atom or a sulfur atom.
 11. The polymeric compound according to claim 10, wherein said structural unit (a1) comprises at least two types of structural units.
 12. The polymeric compound according to claim 10, wherein said structural unit (a1) comprises at least one member selected from the group consisting of a structural unit represented by general formula (a1-0-11) shown below, a structural unit represented by general formula (a1-0-12) shown below and a structural unit represented by general formula (a1-0-2) shown below:

wherein R represents a hydrogen atom, a lower alkyl group or a halogenated lower alkyl group; R²¹ represents an alkyl group; R²² represents a group which forms an aliphatic monocyclic group with the carbon atom to which R²² is bonded; R²³ represents a branched alkyl group; R²⁴ represents a group which forms an aliphatic polycyclic group with the carbon atom to which R²⁴ is bonded; Y² represents a divalent linking group; and X² represents an acid dissociable, dissolution inhibiting group.
 13. The polymeric compound according to claim 10, wherein the total amount of said structural unit (a0) and said structural unit (a2) within said component (A1′) is 5 to 70 mol %.
 14. The polymeric compound according to claim 10, wherein said structural unit (a2) comprises at least one member selected from the group consisting of a structural unit represented by general formula (a2-1) shown below and a structural unit represented by general formula (a2-2) shown below:

wherein R represents a hydrogen atom, a lower alkyl group or a halogenated lower alkyl group; each R′ independently represents a hydrogen atom, an alkyl group of 1 to 5 carbon atoms, an alkoxy group of 1 to 5 carbon atoms or —COOR″, wherein R″ represents a hydrogen atom or an alkyl group; R²⁹ represents a single bond or a divalent linking group; s″ represents an integer of 0 to 2; and A″ represents an oxygen atom, a sulfur atom or an alkylene group of 1 to 5 carbon atoms which may contain an oxygen atom or a sulfur atom.
 15. The polymeric compound according to claim 10, wherein said component (A1′) further comprises said structural unit (a1).
 16. The polymeric compound according to claim 10, which further comprises a structural unit (a3) derived from an acrylate ester containing a polar group-containing aliphatic hydrocarbon group. 